Phillip Scheinberg, Neal S. Young and Johnson M. Liu
ACQUIRED BONE MARROW FAILURE SYNDROMES
The bone marrow failure syndromes are characterized by inadequate blood cell production leading to low red blood cell, white blood cell, and/or platelet counts in the peripheral blood. Marrow failure can be acquired or constitutional, and may affect all three blood cell lines, resulting in pancytopenia, or only a single lineage. In most, the bone marrow shows a simple deficiency of the related precursor cells, but marrow failure can also occur with relatively cellular marrows, presumably due to ineffective hematopoiesis, and be associated with cytogenetic abnormalities (see the chapter on myelodysplastic syndromes (MDSs)) or a genetically altered cell, as in paroxysmal nocturnal hemoglobinuria (PNH), discussed in this chapter because of its intimate relationship to aplastic anemia (AA).1 Even the paradigmatic syndrome of AA clinically and pathophysiologically shows overlap with related diseases (Fig. 6.1).
ACQUIRED APLASTIC ANEMIA
Acquired AA is characterized by pancytopenia with a hypocellular, often empty, bone marrow. AA is uncommon in the West: its incidence in Europe is about two new cases per million of population. However, the disease is two- to three fold more frequent in East Asia and probably elsewhere in the developing world. In most series, patients are young with the majority presenting between 15 and 25 years of age. Historically, chemicals (benzene) and medical drugs (chloramphenicol) were implicated as causative, but without satisfactory mechanisms of pathogenesis. The most important current associations are with nonsteroidal anti-inflammatory drugs, antithyroid drugs, penicillamine, allopurinol, and gold (Table 6.1).2 Nonetheless, most AA is idiopathic, and it is usually not possible to assign an environmental cause in an individual patient. One objective association is with prior seronegative hepatitis, present in 5% to 10% of patients in most case series.
FIGURE 6.1 Venn diagram of the relationship among bone marrow failure syndromes. AA, aplastic anemia; AML, acute myeloid leukemia; DKC, dyskeratosis congenita; MDS, myelodysplasia; PNH, paroxysmal nocturnal hemoglobinuria; SDS, Shwachman-Diamond syndrome.
Table 6.1 Drugs Associated with Aplastic Anemia in the International Aplastic Anemia and Agranulocytosis Study
Nonsteroidal analgesics
Butazones
Indomethacin
Piroxicam
Diclofenac
Antibiotics
Sulfonamides†
Antithyroid drugs
Cardiovascular drugs
Furosemide
Psychotropic drugs
Phenothiazines
Corticosteroids
Penicillamine
Allopurinol
Gold
†Other than trimethoprim-sulfonamide combination.
Etiology and Pathophysiology
Hematopoiesis is severely reduced in all AA, as observed in bone marrow specimens, CD34 cell counts, magnetic resonance imaging, or in colony culture assays of progenitors.
Clinical and laboratory studies suggest that most acquired AA is secondary to immunologically mediated destruction of hematopoietic cells by cytotoxic lymphocytes (CTL) and their cytokine products, especially interferon-γ(IFN-γ) and tumor necrosis factor-α (TNF-α).
Marrow failure rarely can follow infectious mononucleosis (Epstein-Barr virus [EBV] infection) and is a component of the stereotypical post-hepatitis AA syndrome. EBV and the putative agent of seronegative hepatitis likely behave as triggers for immune system activity. In contrast, parvovirus B19 directly infects and kills erythroid progenitor cells and causes transient red cell aplasia and occasionally chronic pure red cell aplasia (PRCA), but not AA.
Direct killing of marrow cells by cytotoxic agents occurs following cancer chemotherapy, producing transient marrow aplasia, but is probably unusual as a mechanism of idiosyncratic drug-associated AA.
Clinical Features
Anemia leads to fatigue, weakness, lassitude, headaches, and in older patients dyspnea and chest pain and these symptoms are most commonly responsible for the clinical presentation.
Thrombocytopenia produces mainly mucosal bleeding: petechiae of the skin and mucous membranes, epistaxis, and gum bleeding are frequent and early complaints. Bleeding is not brisk from low platelets unless in the presence of accompanying physical lesions, as in gastritis and fungal infection of the lungs. The most feared complication of thrombocytopenia is intracranial hemorrhage.
Infection is unusual at presentation.
Dark urine suggests PNH.
Occasionally, moderate cytopenias are identified serendipitously by routine blood work or at preoperative evaluation.
Constitutional symptoms (malaise, anorexia, and weight loss) should be absent.
Physical findings range from a well appearing patient with minimal findings to an acutely ill patient with signs of systemic toxicity. Cachexia, lymphadenopathy, and splenomegaly are not seen and suggest an alternative diagnosis.
Thrombocytopenia results in petechiae, ecchymoses, gingival oozing, epistaxis, and subconjunctival and retinal hemorrhage.
Anemia is reflected in pallor of the skin, mucous membranes, and nail beds.
Constitutional AA is suggested by areas of hyper- or hypopigmentation of the skin, abnormal hands and thumbs, short stature (Fanconi anemia [FA]), and nail dystrophy and oral leukoplakia (dyskeratosis congenita [DKC]).
Diagnosis and Differential Diagnosis
At diagnosis:
Marked pancytopenia or reduction in two of three or, less commonly, one of three cell lines
Peripheral blood smear shows reduced platelets and neutrophils, normal red cells
Microspherocytes and giant platelets suggestive of peripheral destruction are not present
Bone marrow markedly hypocellular on biopsy (1 cm core); mainly residual lymphocytes, plasma cells, mast cells on aspirate smear
Overall marrow biopsy cellularity is low (<30%, excluding lymphocytes), but there may be pockets
of cellularity, so-called hot-spots.
Myeloblasts should not be increased
Megakaryocytes are almost always absent
Marrow cytogenetics should be normal, but some authorities accept cytogenetic abnormalities such as trisomy 6 or 8, loss of Y or del20q as consistent with AA in the absence of significant dysplastic marrow findings.
In secondary marrow failure, the degree of pancytopenia is usually moderate, and the underlying illness is usually obvious from history and physical examination (e.g., stigmata of alcohol liver disease, presence of other autoimmune disease or infection). However, pancytopenia has many causes, of which AA is not the most common (Table 6.2).
Table 6.2 Differential Diagnosis of Pancytopenia
Pancytopenia with Hypocellular Bone Marrow
Acquired aplastic anemia
Inherited aplastic anemia
Some myelodysplastic syndromes
Rare aleukemic leukemia
Some acute lymphoblastic leukemia
Some lymphomas of the bone marrow
Pancytopenia with Cellular Bone Marrow
Primary Bone Marrow Diseases
Myelodysplasia syndromes
Paroxysmal nocturnal hemoglobinuria
Myelofibrosis
Hairy cell leukemia
Some aleukemic leukemia
Myelophthisis
Bone marrow lymphoma
Secondary to Systemic Diseases
Systemic lupus erythematosus, Sjögren’s syndrome
Hypersplenism
Vitamin B12, folate deficiency (familial defect)
Overwhelming infection
Alcoholism
Brucellosis
Ehrlichiosis
Sarcoidosis
Tuberculosis and atypical mycobacteria
Hypocellular Bone Marrow with or without Cytopenia
Q fever
Legionnaire’s disease
Toxoplasmosis
Mycobacteria
Tuberculosis
Anorexia nervosa, starvation
Hypothyroidism
Most important is to distinguish among primary marrow diseases (Table 6.3, Fig. 6.2):
Constitutional AA presenting in adults. A family history is highly suggestive. FA pedigrees often have instances of leukemias and myelodysplasia (MDS); telomeropathy families often include not only malignant hematologic diseases but also pulmonary fibrosis and hepatici cirrhosis. There may be no or only subtle physical stigmata. Patients under 40 years of age (or older if the history or examination are suggestive) should be tested for FA. Although phenotypic abnormalities have been classically described in both FA and DKC, patients with adult onset constitutional AA may have subtle signs on routine physical examination or no characteristic findings at all. 3
MDS is hypocellular in about 20% of cases. Dysplastic changes in AA when present are mild and limited to erythrocytes. In MDS, megaloblastic changes are more extreme; megakaryocytes are preserved and can be aberrantly small and mononuclear; and myeloid precursors may be increased, left shifted, and poorly granulated. Chromosomal analysis of bone marrow cells is almost always normal in AA, while MDS is often associated with cytogenetic abnormalities. Nonetheless, the distinction may be so difficult that some patients are best labeled AA/MDS.
PNH/AA. Small PNH expanded clones are common—in as many as 50% of cases at presentation—in the setting of marrow failure now that flow cytometry has replaced the Ham test. Growth of clone size over time may lead to clinical hemolysis. Thrombosis is rare.
Acute lymphocytic leukemia in children and acute myeloid leukemia in the elderly can occasionally present with pancytopenia and marrow hypocellularity.
Myelofibrosis has a characteristic leukoerythroblastic blood picture, marrow is dry tap (rather than watery, as in AA), and hepatosplenomegaly is common.
Large granular lymphocytosis is characterized by prolonged neutropenia, less frequently anemia or thrombocytopenia, and increased numbers of large granular lymphocytes in the peripheral blood. Marrow is usually cellular; diagnosis rests on flow cytometry or molecular evidence of rearrangement of the T cell receptor.
Severe AA is defined by two of the following three peripheral blood count (Camitta) criteria
absolute neutrophil count (ANC) <500/µL
platelet count <20,000 /µL
reticulocyte count (automated) <60,000/µL
Definitive Treatments
Definitive therapy of AA consists of allogeneic hematopoietic stem cell transplantation (HSCT) or immunosuppression; both have dramatically changed the natural course of this illness, with 5 year survival of 75% in patients undergoing either treatment.4 Support with growth factors alone or in combination with transfusion is of unproven long-term benefit and is unlikely to address the underlying pathophysiology of the disease. The main distinctions between immunosuppression and HSCT are shown in Table 6.4.
FIGURE 6.2 Differential diagnosis of cytopenias. MDS, myelodysplastic syndrome; BM, bone marrow; PNH, paroxysmal nocturnal hemoglobinuria.
HSCT cures AA. Most transplants are performed using a histocompatible sibling donor, and most recipients are young. Overall long-term survival is about 70% to 80%, with better results observed in children.5,6 HSCT is preferred in children to about age 20 who have an appropriate donor. With current cyclophosphamide-based conditioning, major toxicities are related to graft-versus-host disease (GVHD) and infection (not always easily separable). GVHD and mortality risk increases with recipient age.5 The source of donor cells may be important: in recent retrospective studies, granulocyte colony stimulating factor (G-CSF)-mobilized stem cells produced a higher rate of chronic GVHD and mortality in younger patients than did bone marrow cells.7,8 Modest numbers of erythrocyte and platelet transfusions do not appear to increase the risk of graft rejection, especially with leukocyte-depleted products.9
Seventy percent of patients will lack a suitable matched sibling donor. Transplantation from matched unrelated donors (MUD) is now more feasible with the development of huge donor registries and an effective network. Overall results have been about half as good as with human leukocyte antigen (HLA)-matched family members but likely to improve with modifications of conditioning regimens and high-resolution molecular typing for donor selection10,11; in some small studies, outcomes with alternative donor sources approximate standard transplant outcomes.12,13 Donor searches should be initiated early for younger patients who might be eligible later for a MUD. Of note, the success rate for identifying a suitable matched unrelated donor in the United States decreases in non-Caucasian patients such as in the African American and Hispanic ethnic groups. For unclear reasons, umbilical cord blood transplantation has been associated with poor results in marrow failure states.14 In current practice, unrelated transplant is offered for children who have failed a single course of immunosuppression and to adults who are refractory to multiple courses of antithymocyte globulin (ATG) and alternative therapies such as androgens.
Immunosuppression using regimens combining ATG and cyclosporine (CsA) is standard therapy. About 2/3 of patients improve to transfusion-independence and, overall survival rates at 5 years are comparable to HSCT. Immunosuppression is almost always preferred in older patients, especially if the neutrophil count is not severely decreased. One frequently used protocol for horse ATG is 40 mg/kg/day for 4 days. Rabbit ATG is administered at 3.5 mg/kg/day for 5 days Corticosteroids, such as methylprednisolone at 1 mg/kg, are administered during the first 2 weeks to ameliorate serum sickness. In a recent randomized study, hematologic response rate at 6 months was inferior with rabbit ATG (37%) compared to horse ATG (68%) when given as first therapy.15 This large difference in response translated in worst survival at 3 years after rabbit ATG (70%) as compared to horse ATG (94%).16Thus, horse ATG is the preferred initial immunosuppressive treatment in SAA.
In patients who are refractory to initial horse ATG, hematologic recovery can be achieved with a second course of rabbit ATG17; in our institutional experience, about 30% of patients showed a hematologic response.18Alemtuzumab also has activity in SAA primarily in the relapse and refractory settings.19 In relapse, alemtuzumab (without CsA) produced hematologic response in 55% of cases, which is comparable to the reported rates of rabbit ATG in this setting; in refractory SAA, the response rate to alemtuzumab was 37%, which was similar to that of rabbit ATG (33%) in direct comparison.19 As first therapy, alemtuzumab fared poorly, with a response rate of only 19% in a prospective randomized study.19 Thus, alemtuzumab may be an option in relapsed and refractory SAA, especially in those intolerant to ATG and/or CsA, or in older patients.
Major toxicities of ATG include immediate allergic reaction, serum sickness, and transient blood count depression. Anaphylaxis is rare but has been fatal and may be predictable by skin testing. Treatment of ATG allergy is mainly symptomatic: intravenous hydration, antihistamines (for urticaria) and meperidine (for rigors), and increased doses of corticosteroids (for symptomatic serum sickness). CsA is begun at 10 mg/kg in adults and 12/mg/kg in children, with dose adjustments to maintain blood levels about 200 ng/mL. We administer CsA for 6 months following ATG. It is common for CsA to be tapered after 6 to 12 months with limited data to support this practice. A retrospective Italian study suggested that a CsA taper may be of benefit in preventing relapse, but in our experience in about 70 responders who had their CsA tapered prospectively from 2003 to 2010, we did observe a delay in the occurrence of relapse but did not ultimately prevent it when compared to historical control.15,20 Renl and liver function monitoring is required to avoid nephrotoxicity; hypertension, gingival hypertrophy, and tremulousness which are common side effects. Alemtuzumab is usually well tolerated with infusion-related toxicities more manageable than with ATG. In AA, while immunosuppression (ATG, alemtuzumab) reactivates latent herpes virus infection and increases EBV and cytomegalovirus (CMV) virus in the circulation, disease is rare and routine prophylactic or preemptive antiviral therapy is not required.19,21
Prognosis is strongly correlated to hematologic response at 3 months, especially the robustness of blood count recovery defined by absolute reticulocyte and platelet.22 Pre-therapy, the absolute reticulocyte has also been correlated with a better response rate and survival.23,24 In a recent analysis, the neutrophil count did not correlate with hematologic response outcomes but associated to short-term mortality.25Despite the lack of progress in developing more efficacious immunosuppressive regimens, survival in SAA has improved over the years, especially among non-responders to an initial course of horse ATG, with survival in 5 years increasing nearly three fold among this group (from 23% in the 1990s to 57% in recent years).25 This improvement has been attributed to better supportive care (with antifungals) and more effective salvage therapies with repeat immunosuppression and salvage HSCT. Rates of graft rejection and survival have also improved over time with better transplantation and supportive care protocols, less immunogenic blood products, and closer HLA matching between unrelated donors and recipients with high-resolution tissue typing.13,26-28 However, rates of acute and chronic GVHD have remained steady over the years. A bone marrow source of stem cells (compared to mobilized peripheral blood CD34+ cells) and conditioning with alemtuzumab have been associated with lower rates of GVHD.7,8,29
Even after hematologic response to ATG, blood counts may fall, especially on withdrawal of CsA. Reinstitution of CsA usually suffices, but retreatment with ATG may be necessary and relapse is sometimes irreversible and fatal. Evolution to a clonal hematologic disease occurs in about 15% of patients over the decade after initial therapy, manifesting as a dysplastic bone marrow or cytogenetic abnormalities, especially monosomy 7. Pre-treatment telomere length may identify increased risk for clonal evolution long-term. In a recent report, patients with the shortest telomere length (adjusted for age) had a three fold higher risk of acquiring a new cytogenetic abnormality, and five- to six fold higher for monosomy 7 and complex cytogenetics, when compared to those with longer pre-treatment telomere length. These differences translated into a survival disadvantage associated with short telomeres (66%) compared to long (84% in 6 years).
Other therapies that are occasionally successful include growth factor combinations (erythropoietin and G-CSF), androgens, and high dose cyclophosphamide (controversial due to the prolonged neutropenia that it induces).30 Our approach to treatment is shown in Figure 6.3.
PAROXYSMAL NOCTURNAL HEMOGLOBINURIA
PNH is a rare clonal disease of the bone marrow, which can produce a clinical triad of (1) hemolysis, (2) venous (and rarely arterial) thrombosis, and (3) AA.31
Etiology and Pathophysiology
A somatic mutation in a gene called PIG-A occurs in a hematopoietic stem cell
Leads to deficient synthesis of a glycolipid moiety called the glycosylphosphoinositol anchor (GPI).
FIGURE 6.3 Treatment of severe aplastic anemia. ANC, absolute neutrophil count; ATG, antithymocyte globulin; BM, bone marrow; CsA, cyclosporine A; HSCT, hematopoietic stem cell transplantation; MUD, matched unrelated donor.
Lack of cell surface presentation of a large family of GPI-linked proteins
Absence of one of these proteins, CD59, on the cell surface of erythrocytes leads to their susceptibility to complement and to intravascular hemolysis
PIG-A mutant cells are probably present in normal adult marrow, but clonal expansion of these cells is unusual—except especially in AA (about 50% of cases) and in MDS, where they may range in size from small to large.
Which GPI-anchored proteins are important in permitting clonal expansion in AA and MDS and in the thrombotic proclivity is unknown.
Clinical Features
Intravascular hemolysis, classically as periodic bouts of dark urine in the morning but also as continu-
ous red cell destruction and without hemoglobinuria.
Venous thrombosis in unusual sites, especially hepatic, mesenteric, and portal veins and intracranial veins.
Marrow failure, frank AA or poor marrow function despite a relatively cellular histology.
Diagnosis
In general, intravascular hemolysis is unusual (see Chapter 3), and PNH should be considered in the setting of a suggestive history, hemoglobinuria, and elevated LDH. There may be accompanying iron deficiency and neutropenia/thrombocytopenia.
PNH patients can present with abdominal pain due to Budd-Chiari syndrome or symptoms of stroke.
PNH clonal expansion should be sought in patients with AA and MDS. Peripheral blood Flow cytometry provides evidence of a PNH clonal expansion through quantification of GPI-anchored proteins on erythrocytes and granulocytes (especially the latter in the transfused patient). However, severe hemolysis and thrombosis typically occur only in patients with large clones (>50% erythrocytes).
Treatment
The course is highly variable where clone size may range from small and inconsequential clinically to large and associated with clinical hemolysis. AA patients post-immunosuppressive therapy with expanded clones may be asymptomatic; modest and intermittent hemolysis managed with transfusions alone is consistent with long survival; conversely, PNH can be associated with catastrophic thrombotic events. Clones may spontaneously disappear in some patients.
Transfusion to maintain hemoglobin levels consistent with full activity. Use of washed erythrocytes is not necessary.
Iron supplementation may be required; loss of hemoglobin as a result of intravascular destruction prevents secondary hemochromatosis.
Corticosteroids, usually in moderate doses (30 to 50 mg prednisone on alternate days) have been employed to control hemolysis but never rigorously tested. A short trial in a patient with continuous red cell destruction may be warranted.
Marrow failure presenting as frank AA with associated PNH should be treated with HSCT or immunosuppression (see above).
Most patients in Western series die of thrombotic complications, and thromboses, once they occur, may be refractory to anticoagulation. An uncontrolled trial has suggested that coumadin prophylaxis is effective, but the relative risk of hemorrhage secondary to chronic anticoagulation for years, even decades, in this population remains unclear. 32
HSCT is the only curative therapy, but may carry a higher risk in PNH due to comorbid conditions; nonmyeloablative conditioning regimens may offer improved survival.9 Transplant can be considered in younger patients with severe marrow failure or thrombotic complications.
Eculizumab (a monoclonal antibody directed to the active component of C5) has been approved by the FDA for patients with PNH and is marketed as Soliris. In a large prospective multicenter trial, the drug blocked intravascular hemolysis, which translated to a clinically significant improvement in anemia, transfusion requirements, and in quality of life measures.33 Eculizumab also appeared to dramatically reduce the risk of clinical thromboses in patients with PNH, which is the major cause of morbidity and mortality in this disease.34
PURE RED CELL APLASIA
PRCA is defined as anemia with absent reticulocytes and marrow erythroid precursor cells.35 This rare aregenerative anemia has a number of clinical associations and is also usually responsive to treatment.
Etiology and Pathophysiology
Constitutional PRCA is Diamond-Blackfan anemia (DBA) and is secondary to inherited mutations in ribosomal protein genes.
Acquired PRCA often behaves as an immunologically mediated disease. Clinical associations include thymoma (but probably <10% of PRCA cases), collagen-vascular syndromes, myasthenia gravis, chronic lymphocytic leukemia, and large granular lymphocytic leukemia.
PRCA may also be seen in MDS, especially with 5q-syndrome. The phenotype is due to acquired loss of a ribosomal protein gene on chromosome 5, as occurs in the germline in DBA.
Parvovirus B19 infection causes erythema infectiosum (fifth disease) in children and transient aplastic crisis in patients with underlying hemolysis. Virus infection is ordinarily terminated by production of neutralizing antibodies. Persistence of parvovirus results from failure to mount a neutralizing antibody response, leading to chronic erythroid precursor destruction and anemia. Persistence of parvovirus B19 can occur in an immunodeficient host: in congenital immunodeficiencies (Nezelof ’s syndrome), iatrogenic (immunosuppressive drugs and cytotoxic chemotherapy), and HIV infectioninduced immunodeficiency.
Clinical Features and Diagnosis
Reticulocytes are very low or absent; erythroid precursor cells are usually absent but a few normoblasts may be present in the marrow. There are morphologic clues: giant pronormoblasts signal parvovirus; uninuclear micromegakaryocytes, 5q-syndrome. Other blood counts are normal, as are cytogenetics (except for PRCA associated with MDS).
Thymoma should be excluded by CT scan.
In persistent parvovirus infection and PRCA, antibodies to virus are usually absent, or only IgM may be observed; virus can be detected in the blood by DNA hybridization.
Treatment
For DBA, corticosteroids are standard; patients may be dependent on exquisitely low doses, and relapse may not always be responsive to reinstitution of treatment.
For acquired PRCA, corticosteroids in moderate doses are usually first therapy, followed by either other immunosuppressives such as CsA, ATG, or cytotoxic drugs such as moderate doses of azathioprine or cyclosphosphamide, administered orally. In a few case reports the monoclonal antibodies to CD20 (rituximab) and CD25 (daclizumab) have been shown effective and more recently (in a few case reports) or cyclophosphamide. 36
Thymomas should be excised as they are locally invasive, but surgery does not necessarily resolve the anemia.
Persistent parvovirus B19 infection responds to intravenous immunoglobulins at 0.4 g/kg daily for 5 to 10 days. Patients with large viral loads, especially in the acquired immunodeficiency syndrome, may relapse and require periodic retreatment.
AGRANULOCYTOSIS
Severe neutropenia with either complete or partial absence of myeloid precursor cells is agranulocytosis.
Etiology and Pathophysiology
Most agranulocytosis is drug-associated (Table 6.5). Idiopathic pure white cell aplasia (without exposure to a suspicious drug) is exceedingly rare (and like PRCA may also be associated with thymoma). 37,38
Mechanisms of drug destruction of granulocyte precursors include direct effects (as with thorazine) and immune (antibody)-mediated (as with dipyrone) (Table 6.6).
Table 6.5 Drugs Associated with Agranulocytosis
Heavy metals
Gold
Arsenic compounds
Analgesics
Aminopyrine, dipyrone
Butazones
Indomethacin
Ibuprofen
Acetaminophen
Para-aminosalicylic acid
Sulindac
Antipsychotics, sedatives, antidepressants
Phenothiazines
Tricyclics
Chlordiazepoxide
Barbiturates
Serotonin reuptake inhibitors
Anticonvulsants
Phenytoin
Ethosuximide
Carbamazepine
Antithyroid drugs
Propylthiouracil
Methimazole
Cardiovascular drugs
Procainamide
Captopril
Nifedipine
Quinidine
Propranolol
Methyldopa
Propafenone
Aprinidine
Sulfa drugs
Thiazide diuretics like spironolactone and
acetazolamide
Oral hypoglycemics
Sulfasalazine
Dapsone
Sulfa antibiotics
Antibiotics
Sulfa antibiotics
Pyrimethamine
Penicillins
Cephalosporins
Macrolides
Vancomycin
Clindamycin
Aminoglycosides
Antituberculosis agents
Levamisole
Antimalarials
Mebendazole
Antifungals
Fluconazole
Antiviral
Zidovudine
Antihistamines
Cimetidine
Ranitidine
Chlorpheniramine
Miscellaneous
Isotretinoin
Omeprazole
Colchicine
Allopurinol
Aminoglutethimide
Metoclopramide
Ticlopidine
Tamoxifen
Penicillamine
Insecticides
Hair dye
Chinese herbal medicines
Diagnosis and Treatment
The patient is usually older with a history of clear exposure to an incriminated agent, usually with introduction of the drug in the preceding 6 months. Absent neutrophils on smear should lead to a confirmatory bone marrow examination.
Classic presentation is fever and sore throat.
Recovery occurs spontaneously but over a highly variable time period, from a few days to several weeks. G-CSF or granulocyte monocyte colony-stimulating factor (GM-CSF) is almost always administered without clear evidence of efficacy.
Fever and signs of infection require prompt administration of broad spectrum antibiotics by a parenteral route.
Mortality remains substantial (about 10%) due to the combination of patient age, comorbid conditions, and lethal sepsis.
CONSTITUTIONAL BONE MARROW FAILURE SYNDROMES
Among the constitutional disorders that present with AA, it is important to consider FA and DC. Genes mutated in FA and in DC have been identified and are important in the functions in the cell; they have a key role in genomic stability and the maintenance of telomeres, respectively. An algorithm for laboratory testing to exclude FA and DC is presented below.
FANCONI ANEMIA
Autosomal recessive or X-linked inheritance; most common of the constitutional syndromes, seen in all races; diagnosed on the basis of positive chromosome breakage test (see below)
Mutations in any of these 15 genes: FANCA, FANCB, FANCC, FANCD1/BRCA2, FANCD2, FANCE, FANCF, FANCG, FANCI, FANCJ/BACH1/BRIP1, FANCL, FANCM, FANCN/PALB2, FANCO, FANCP
Chief criteria of pancytopenia, hyperpigmentation, malformation of the skeleton, small stature, and hypogonadism
Malformations of the eye, ear, genitourinary and gastrointestinal tracts, and cardiopulmonary and central nervous systems can occur.
FA is notoriously heterogeneous in the degree and number of clinical manifestations, and patients presenting solely with either congenital malformations or hematologic abnormalities may either be misdiagnosed or go unrecognized entirely.
Clinical Features
The diagnosis is suggested when a child presents with hyper- or hypo-pigmented skin lesions; short stature (poor growth); anomalies of the upper limb or thumb; male hypogonadism; microcephaly; characteristic facial features, including a broadened nasal base, epicanthal folds, and micrognathia; and structural renal abnormalities. When this constellation of physical anomalies is accompanied by bone marrow failure (which may often trigger initial medical evaluation), confirmation of the diagnosis can be made by standard DEB or MMC chromosome breakage analysis (see below).
The mean age at diagnosis 8 to 9 years.
Diagnostic Tests
Chromosome breakage test with diepoxybutane (DEB) or mitomycin C (MMC), performed on peripheral blood cells.
Based solely on definition by the DEB test, nearly 40% of patients may be free of major physical anomalies. These FA patients with normal appearances may go unrecognized unless there is a high index of suspicion for familial disease.
A challenge is the diagnosis of FA in older patients. Although the mean age of diagnosis is in the first decade of life, FA has been described in the 5th and 6th decades of life.
Hematologic Presentations and Cancer Predisposition
The symptoms and signs of FA typically relate to the hematologic presentation of cytopenias from marrow failure. Often, thrombocytopenia or leukopenia is noted before full pancytopenia; furthermore, the pancytopenia typically worsens with time. Almost all FA patients will develop hematologic abnormalities in their lifetime. Erythropoiesis is usually macrocytic.
Classically, the bone marrow is hypocellular and fatty, indistinguishable from that of acquired AA. Microscopic examination of the marrow may show dyserythropoiesis and dysplasia. Some patients may develop or even present with a morphologically defined MDS or frank acute myeloid leukemia (AML).
The crude risk of leukemia (exclusive of MDS) is ∼5% to 10%, while the cumulative incidence of leukemia is about 10% by age 25. Less commonly recognized is the probability of developing MDS, approximately 5%, which appears also to correlate with a poor prognosis for FA patients. Clonal karyotypic abnormalities, identical to those seen in non-FA MDS and secondary AML, are frequently found in FA patients, whether or not they meet marrow morphologic criteria for a defined MDS. The prognostic significance of these clonal chromosomal abnormalities in FA patients is not entirely clear, however, since cytogenetic changes can fluctuate over time. Certain clonal abnormalities may be associated with poor prognosis, such as gains of chromosome 3q.
Solid organ malignancies occur frequently, with a crude risk of 5% to 10% of patients overall (the risk increases with age, as those patients who have survived into adulthood develop solid tumors). Particularly common are vulvar, esophageal, and head and neck cancers. In addition to these (presumed) de novo tumors, a subset of long-term survivors of SCT will develop secondary malignancies, typically head and neck.
For FANCD1/BRCA2 and FANCN/PALB2, as has been demonstrated thus far, affected family members with monoallelic mutations are predisposed to breast cancer, whereas those with biallelic mutations present with an FA phenotype associated with childhood cancers and leukemia.
Stem Cell Transplantation and Supportive Care
Allogeneic SCT from an HLA-matched sibling donor is the only curative therapy for the hematologic manifestations of FA (aplasia or MDS). Typically, decreased doses of cyclophosphamide and irradiation must be used in order to avoid severe toxicity due to the chemo- and radio-sensitivity of FA patients. Transplantation centers, which generally adopted this modified conditioning regimen with or without thoracoabdominal irradiation, have reported good results for FA patients that did not present with leukemia or pre-leukemic transformation.
Umbilical cord blood transplantation from related donors has also been successfully applied to a small number of FA patients. A few FA patients have also undergone successful HSCT with cord blood from unrelated donors.
Clearly, young patients with an HLA-compatible sibling should be treated by HSCT at the earliest stages of marrow failure in preference to other therapies. However, most patients do not have an HLA-identical donor and are dependent upon the identification of a suitably matched nonsibling relative or unrelated donor. A smaller number of FA patients have undergone HSCT from such alternative sources (matched unrelated and haploidentical family donors) to treat either aplasia or MDS, with or without clonal chromosomal abnormalities. The results from these alternative donor transplants have generally been inferior to those from matched sibling donor transplants, but are improving.
Patients lacking a suitable HLA-compatible donor (either sibling or matched unrelated) may benefit from chronic administration of androgens or hematopoietic growth factors, which may serve as temporizing measures.
Androgens
Androgens have been shown to induce hematologic responses in approximately 50% of FA patients although their effectiveness in raising blood counts may be neither durable nor complete in all lineages. Typically, androgen therapy is initiated when the platelet count is consistently below 30,000/µL and/or the hemoglobin less than 7 gm/dL. Orally administered oxymetholone, at a dose of 2 to 5 mg/ kg/day, is usually combined with prednisone, 5 to 10 mg every other day, in order to counterbalance the anabolic properties of oxymetholone with catabolic actions of corticosteroids.
Androgen therapy is associated with liver toxicities including transaminase enzyme elevation, cholestasis, peliosis hepatitis, and hepatic tumors.
Hematopoietic Growth Factors
Levels of most growth factors are markedly increased in FA as they are in acquired AA, likely as a compensatory physiologic response.
One worrisome aspect of chronic growth factor administration is the theoretical risk of stimulating a leukemic clone, particularly in patients prone to developing MDS or AML, or speeding the process of stem cell exhaustion.
Chronic administration of G-CSF may have transient beneficial effects on multiple hematopoietic lineages in some patients.
DYSKERATOSIS CONGENITA
Classical DKC is an inherited bone marrow failure syndrome characterized by the muco-cutaneous triad of abnormal skin pigmentation, nail dystrophy, and mucosal leukoplakia.
It has been observed in many races and estimated prevalence of DKC is approximately 1 per 1,000,000 persons.
X-linked recessive (mutations in DKC1), autosomal dominant (some cases due to heterozygous mutations in the RNA component of telomerase, TERC), and autosomal recessive (some cases due to NOP10gene mutations) forms of the disease are recognized. Heterozygous mutations in the enzymatic component of telomerase (TERT) as well as in TERC can lead to variable phenotypes.
A variety of other (dental, gastrointestinal, genitourinary, hair greying/loss, immunological, neurological, ophthalmic, pulmonary, and skeletal) abnormalities have also been reported.
Bone marrow failure is the principal cause of early mortality with an additional predisposition to malignancy and fatal pulmonary complications
Clinical manifestations in DKC often appear during childhood although there is a wide age range. The skin pigmentation and nail changes typically appear first, usually by the age of 10 years. BM failure usually develops below the age of 20 years; 80% to 90% of patients will have developed BM abnormalities by the age of 30 years. In some patients the BM abnormalities may appear before the muco-cutaneous manifestations and can lead to an initial diagnosis of idiopathic AA.
The clinical features of these disorders are very heterogeneous and this makes diagnosis based on clinical criteria alone difficult and unreliable. In many pedigrees, disease only manifests in adulthood, hematologic manifestations can range from severe AA and AML to mild macrocytosis, and affected members may only have lung or liver disease.
Oxymetholone can produce durable hematological responses in more than >50% of DKC and FA patients, but patients have to be monitored carefully for side effects. Androgens may function by increasing TERT transcription.
The current definitive treatment is allogeneic HSCT. In both DKC and FA patients, low-intensity transplant protocols are producing prompt engraftment, reduced toxicity, and have the potential to reduce the risk of secondary malignancies.
Diagnostic Testing for Aplastic Anemia with Short Telomeres
Telomeres are the tips of chromosomes and are maintained by a complex that includes the enzyme telomerase reverse transcriptase (TERT), its RNA component (TERC), the protein dyskerin, and other associated proteins (NHP2, NOP10, and GAR1). Telomere length measurement is now commercially available and should be a screening test in most cases of severe AA, especially with a typical clinical history (moderate, slowly progressive AA) or if the family history suggests an inherited syndrome.
AA with short telomeres is typical in DKC patients. Since the genes mutated in the X-linked recessive (DKC1) and other (TERC and others) DKC subtypes are now known, it is possible to substantiate the diagnosis in a significant proportion of DKC patients. In particular, it is appropriate to screen for the DKC1 gene if patients are male and have two out the following: abnormal skin pigmentation, nail dystrophy, leukoplakia, or bone marrow failure.
Besides patients with a typical DKC pedigree, however, there are also patients with acquired AA with short telomeres who can carry mutations in TERT and TERC and not have the physical abnormalities observed in DKC or have a family history suggestive for telomeropathy. Overall, mutations in telomerase genes (TERC or TERT but not DKC1) appear to explain the short telomeres detected in about 10% of patients with AA with some responding to conventional immunosuupressive therapy as is applied in acquired AA cases. The failure of organs other than the bone marrow, including the liver and the lung, may also be associated with TERT mutations.
Marrow Failure Involving a Single Lineage
DIAMOND-BLACKFAN ANEMIA
Probably the second most common constitutional marrow failure syndrome after FA
Most patients present with anemia in the neonatal period or in infancy.
Approximately 30% of affected children present with a variety of associated physical anomalies. Thumb and upper limb malformations and craniofacial abnormalities are common. Other defects: atrial or ventricular septal defects, urogenital anomalies, and prenatal or postnatal growth retardation.
A moderately increased risk of developing MDS and solid organ malignancies
Cases are sporadic, with an equal sex ratio, but 10% to 25% of patients have a positive family history for the disorder.
Heterozygous mutations in the ribosomal protein genes RPS19, RPS24, RPS17, RPS6, RPS10, RPS26, RPL5, RPL11, and RPL35A account for some cases.
Hematological Findings
Minimal diagnostic criteria for DBA: normochromic anemia in infancy (<2 years), low reticulocyte counts, absent or decreased bone marrow red cell precursors (<5% of nucleated cells), and a normal chromosome breakage test (to rule out FA)
Additional features: presence of malformations, macrocytosis, elevated fetal hemoglobin (HbF), and elevated erythrocyte adenosine deaminase (eADA) level
Some patients identified after the age of 2 years after a more severely affected family member first diagnosed
Anemia usually severe at the time of diagnosis (usually macrocytic)
The bone marrow aspirate is usually normocellular, but erythroblasts are markedly decreased or absent. The other cell lines are normal, but mild to moderate neutropenia, thrombocytopenia, or both may occur later in the course.
Progression of the single-lineage erythroid deficiency of DBA into pancytopenia and AA is rare but may occur.
Differential diagnosis includes transient erythroblastopenia of childhood (TEC). Both TEC and DBA show similar marrow morphology, but TEC is self-limited, with a recovery within 5 to 10 weeks.
Treatment
Initial treatment in DBA is transfusions, but long-term administration of red cells may cause secondary hemochromatosis.
Corticosteroids are the mainstay of treatment, and at least 50% of patients respond. There is no known predictor of steroid responsiveness, and later relapses occur. During treatment, some patients may recover sensitivity to corticosteroids or even proceed to a spontaneous remission.
Allogeneic BMT is a treatment option for DBA in steroid-resistant patients.
Hematopoietic growth factor therapy with interleukin-3 (IL-3) or EPO has been attempted for DBA.
SHWACHMAN-DIAMOND SYNDROME
Probably the third most common constitutional marrow failure syndrome after FA
Autosomal recessive disorder usually manifest in infancy and characterized by exocrine pancreatic insufficiency, short stature, and bone marrow dysfunction
Mutations in the SBDS gene account for about 90% of cases
The SBDS protein appears to be involved in multiple functions, including ribosome maturation
Additional clinical features include: metaphyseal dysostosis, epiphyseal dysplasia, immune dysfunction, liver disease, growth failure, renal tubular defects, insulin-dependent diabetes mellitus, and psychomotor retardation.
Hematological manifestations: neutropenia, raised HbF levels, anemia, thrombocytopenia, impaired neutrophil chemotaxis
Predilection for malignant myeloid transformation and MDS
Clinical Diagnostic Criteria
Clinical Diagnosis
Fulfill the combined presence of hematological cytopenia of any given lineage (most often neutropenia) and exocrine pancreas dysfunction
Hematologic abnormalities may include:
Neutropenia <1.5 × 109/L on at least two occasions over at least 3 months
Hypoproductive cytopenia detected on two occasions over at least 3 months
Pancreatic dysfunction may be diagnosed by the following:
Reduced levels of pancreatic enzymes adjusted to age [fecal elastase, serum trypsinogen, serum (iso) amylase, serum lipase]
Tests that support the diagnosis but require corroboration:
Abnormal 72 hours fecal fat analysis
Reduced levels of at least two fat-soluble vitamins (A, D, E, K)
Evidence of pancreatic lipomatosis (e.g., ultrasound, CT, MRI, or pathological examination of the pancreas by autopsy)
Molecular Diagnosis: Biallelic SBDS Gene Mutation
Positive genetic testing for SBDS mutations known or predicted to be deleterious, for example, from protein modeling or expression systems for mutant SBDS
Treatment
Treatment of hematologic manifestations (neutropenia, bone marrow failure) may involve Hematopoietic growth factor therapy with G-CSF. For neutropenia unresponsive to G-CSF, SAA, MDS, or leukemia, hematopoietic HSCT may be considered.
SEVERE CONGENITAL NEUTROPENIA AND CYCLIC NEUTROPENIA
Originally described as an autosomal recessive disorder (Kostmann syndrome) but majority of SCN cases due to dominant-acting point mutations in the neutrophil elastase (ELANE or ELA2) gene. Mutations in the protooncogene GFI1 that target and repress ELANE have also been implicated.
Characterized by severe neutropenia and an early stage maturation arrest of myelopoiesis, leading to bacterial infections from early infancy
>90% of these patients respond to G-CSF (filgrastim, lenograstim) with ANC that can be maintained around 1.0 × 109/L. Adverse events include mild splenomegaly, moderate thrombocytopenia, osteoporosis, and malignant transformation into MDS/leukemia. Development of additional genetic aberrations (G-CSF-receptor or RAS gene mutations, monosomy 7) during the course of the disease indicates an underlying genetic instability.
Hematopoietic SCT is still the only available treatment for patients refractory to G-CSF.
Cyclic neutropenia (CN), which is also caused by mutations in ELANE, is an autosomal dominant disorder (sporadic or inherited) characterized by regular oscillations of neutrophils from near normal to severely low levels, generally with a 21-day periodicity. ANC nadirs are associated with fever, mouth ulcers, pharyngitis, sinusitis, or more serious infections. CN usually presents early in childhood but be asymptomatic, and transformation to MDS and AML has not been reported. Symptomatic CN is responsive to G-CSF, which typically shortens nadir duration and increases ANC but usually does not ablate cycling.
CONGENITAL AMEGAKARYOCYTIC THROMBOCYTOPENIA
Characterized by severe thrombocytopenia due to a lack of megakaryocytes in the bone marrow from birth
Diagnosis based mainly on the exclusion of other forms of congenital thrombocytopenia with ineffective megakaryopoiesis such as FA.
Molecular basis for this autosomal recessive disorder may be homozygous or compound heterozygous mutations in the c-mpl gene coding for the thrombopoietin receptor.
At time of diagnosis, the bone marrow of congenital amegakaryocytic thrombocytopenia (CAMT) patients is normocellular with a normal representation of all hematopoietic lines except for megakaryocytes. During the course of CAMT, the disease usually evolves into AA.
SCT has been shown to be the only curative therapy.
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