Setting: office
CC: “I just can’t get up out of a chair without using my arms.”
VS: BP:118/74 mm Hg; P: 72 beats/minute; T: normal; R: normal
HPI: A 29-year-old woman comes to the office with several months of progressively worsening muscle weakness. She delayed coming to see you because she just thought it was fatigue and tiredness from working a lot. Over the past week, the weakness worsened to the point where she needs to use her arms to get up out of a chair. The muscles are not painful. Joint pain is present.
“I can’t get up from my seat without using my arms!” = Proximal Muscle Weakness
PMHX: rash on hands and neck
Medications: none
Which of these is usually not painful?
a. Fibromyalgia
b. Polymyositis
c. Polymyalgia rheumatica (PMR)
d. Rhabdomyolysis
Answer b. Polymyositis
Polymyositis-dermatomyositis (PM-DM) is an autoimmune myopathy characterized by weakness in nearly patient, but with pain in <25% of patients. Fibromyalgia and PMR are, by definition, pain disorders. That’s what the word “fibromyalgia” means, “fibrous muscle pain.” As PM-DM progresses, some people develop pain later.
PE:
No fever.
Skin: red-purple rash around her eyes.
Chest: clear to auscultation, V-shaped red rash at top of chest.
Extremities: rough patches on backs of hands.
Musculoskeletal: weakness of shoulders, hips, and girdle; patient cannot easily get up from a seated position without using her hands; muscles are not tender.
Fibromyalgia:
• Focal tenderness
• “Trigger points”
• 100% normal laboratory test results
PMR
• Age >50 years
• Nontender
• ESR high, creatine phosphokinase (CPK) level normal
Initial Orders:
CPK
Aldolase
Lactate dehydrogenase (LDH), aspartate aminotransferase (AST)
ESR
ANA
What is the difference between polymyositis (PM) and dermatomyositis (DM)?
a. ANA positivity
b. Aldolase
c. Skin finding
d. Response to steroids
e. LDH level
Answer c. Skin finding
On presentation, there is no difference between PM and DM. They both have positive ANA and elevated aldolase, CPK, and LDH levels, and they both respond to steroids. There is a difference on pathologic finding on biopsy, but nothing is different on physical findings or symptoms besides skin findings. DM has a vasculopathy with terminal complements C5 to C9 around the vessels. PM has lymphocytes accumulated in muscle fascicles.
Dermatomyositis: C5-C9 around vessels
Polymyositis: lymphocytes around muscle fascicles
DM Skin Effects
• Gottron papules: hands
• Shawl: neck
• Heliotrope: eyes
The patient comes in 3 days to discuss laboratory test results. Muscle weakness is interfering with her ability to navigate train station stairs and travel to your office.
Reports:
CPK: 2450 units/L (elevated)
Aldolase: elevated
ESR: 84 mm/h
ANA: positive
LDH, AST: elevated
Aldolase = Muscle damage
Nonspecific
Which is the most accurate test of dermatomyositis?
a. Muscle biopsy
b. Electromyography (EMG)
c. Anti-Jo
d. Skin biopsy
Answer a. Muscle biopsy
Although skin involvement is the hallmark of dermatomyositis, the most accurate test is a muscle biopsy. EMG is generally recommended even though it is not as specific as a muscle biopsy.
CCS is more “forgiving” on ordering tests. On CCS, get the ANA, AST, ANA, EMG, and ESR.
For single-best-answer questions,
Proximal Weakness without Pain = PM-DM = CPK and Aldolase = Muscle Biopsy
Orders:
EMG
Prednisone orally
Rheumatology consultation if not done
Consult rheumatology on all rheumatologic disorders except OA and gout.
Weakness + CPK and Aldolase Elevation = Enough to Start Therapy
Steroids are the mainstay of PM-DM treatment.
Which of these factors is different in comparing PM with DM?
a. Use of azathioprine
b. Incidence of cancer
c. Dysphagia
d. Lung fibrosis
Answer b. Incidence of cancer
Dermatomyositis confers the risk of cancer much more than polymyositis. Both of them are treated with azathioprine or MTX if steroids are not effective. Both confer a risk of lung fibrosis. Both of them can cause dysphagia. PM and DM are identical on muscle involvement.
On CCS, always do an Interval History a few days after the start of therapy that should improve symptoms. Always confirm symptomatic improvement.
Move the clock forward 3 to 4 days.
Interval history: “Improved muscle weakness. Able to walk up stairs and get up from a seated position without the use of her arms.”
PE: hip, shoulder, and quadriceps flexion and extension
Report:
EMG: abnormal, possible inflammatory myopathy
EMG can reveal the presence of a primary muscle disorder.
EMG cannot specify which disorder the patient has.
Orders:
Muscle biopsy
Muscle biopsy is consistent with dermatomyositis. Continue the patient on steroids and follow up in a few weeks.
Order:
Anti-Jo antibody
• Anti-Jo = Lung Involvement Possible
• It is not clear what to do if Anti-Jo is positive.
The patient returns in 2 weeks. She has developed dysphagia and her muscle strength is somewhat worse.
Orders:
Continue prednisone.
Add azathioprine.
Add trimethoprim-sulfamethoxazole (TMP-SMZ).
Order a colonoscopy.
Order a mammography.
Dysphagia
• Muscle weakness
• Proximal third of the esophagus
• Skeletal muscle
Screen DM patients for cancer.
TMP-SMZ
• Pneumocystis prophylaxis
• For chronic steroid use
• Especially with steroid-azathioprine combination
After 2 to 4 weeks, there is an improvement in muscle strength.
What will you add to treatment if there is worsening on steroids and azathioprine?
a. MTX
b. Rituximab
c. Androgens
d. 6-Mercaptopurine
Answer b. Rituximab
You continue the patient on both medications for now. It is not clear what to do next. Rituximab is, at present, considered the best of the alternative immunosuppressant medications for those with steroid-resistant PM-DM. MTX is an alternative to azathioprine and would never be added. Androgens are not effective for PM-DM.
6-Mercaptopurine is a metabolite of azathioprine. It is, essentially, the same drug with the same effect. Intravenous immunoglobulin (IVIG) is an alternative to rituximab. Other alternatives to add later are:
• Cyclosporine or tacrolimus
• Cyclophosphamide
The treatment of steroid-resistant PM-DM is difficult and unclear. You would not need to know more than:
1. Steroids are given first.
2. Add azathioprine or MTX if steroids are not effective.
3. Rituximab may help later.
The extent of cancer screening is not clear.
Exclude:
• Colon
• Breast
• Ovary