Rheumatology · Inflammatory Myopathies
The facts most likely to be tested
Dermatomyositis presents with symmetric proximal muscle weakness and pathognomonic cutaneous findings including Gottron papules and the heliotrope rash.
The heliotrope rash is a violaceous eruption involving the upper eyelids often accompanied by periorbital edema.
Gottron papules are erythematous to violaceous scaly plaques located over the dorsal interphalangeal joints.
Laboratory evaluation reveals elevated creatine kinase (CK), aldolase, and lactate dehydrogenase (LDH) reflecting skeletal muscle damage.
The most specific autoantibody associated with dermatomyositis is the anti-Jo-1 antibody, which is also linked to interstitial lung disease and mechanic's hands.
Dermatomyositis is a paraneoplastic syndrome with a strong association with underlying malignancy, most commonly ovarian, lung, pancreatic, or colorectal cancer.
The gold standard for diagnosis is a muscle biopsy showing perifascicular atrophy and perimysial inflammation.
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A 58-year-old woman presents with a 3-month history of progressive difficulty rising from a chair and brushing her hair. She reports a persistent, itchy, violaceous rash on her eyelids and scaly red bumps over her knuckles. Physical examination reveals symmetric proximal muscle weakness in the upper and lower extremities. You note a heliotrope rash on the eyelids and Gottron papules on the dorsal MCP and PIP joints. Laboratory studies show a significantly elevated creatine kinase level.
Given the patient's age and clinical presentation, what is the most important next step in management?
Age-appropriate cancer screening (e.g., CT chest/abdomen/pelvis, mammography, colonoscopy)
The patient presents with classic signs of dermatomyositis; because this condition is a well-established paraneoplastic syndrome, the most critical next step is to screen for an underlying occult malignancy.
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Etiology / Epidemiology
Idiopathic inflammatory myopathy with bimodal distribution (ages 5-15 and 40-60). Strong association with underlying malignancy.
Clinical Manifestations
Symmetric proximal muscle weakness and pathognomonic Gottron papules and heliotrope rash.
Diagnosis
Muscle biopsy is the gold standard. Elevated creatine kinase (CK) and anti-Jo-1 antibodies.
Treatment
High-dose corticosteroids are first-line. Avoid sun exposure and screen for occult cancer.
Prognosis
High risk of interstitial lung disease and malignancy (ovarian, lung, GI).
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Epidemiology & Etiology
Affects women twice as often as men. It is an autoimmune condition characterized by immune-mediated damage to skeletal muscle and skin. A significant subset of patients, particularly older adults, harbor an occult malignancy.
Pertinent Anatomy
Targets the proximal muscle groups (shoulders and hips) leading to difficulty rising from chairs or combing hair. Skin involvement typically targets the face, neck, and extensor surfaces of joints.
Pathophysiology
Involves CD4+ T-cell mediated injury to the microvasculature of the perimysium. Complement-mediated damage leads to muscle fiber necrosis and atrophy. The process is often triggered by environmental factors in genetically susceptible individuals.
Clinical Manifestations
Patients present with painless, symmetric proximal muscle weakness. Look for the heliotrope rash (violaceous eyelid discoloration) and Gottron papules (scaly, erythematous plaques over knuckles). Dysphagia and interstitial lung disease are critical systemic red flags.
Diagnosis
The muscle biopsy shows perimysial inflammation and perifascicular atrophy. Laboratory findings include elevated creatine kinase (CK) and aldolase. Serology often reveals anti-Jo-1 (antisynthetase syndrome) or anti-Mi-2 antibodies.
Treatment
High-dose oral prednisone is the initial treatment of choice. If refractory, use methotrexate or azathioprine as steroid-sparing agents. Hydroxychloroquine is used specifically for refractory skin lesions.
Prognosis
Patients require age-appropriate cancer screening (colonoscopy, mammography, CT chest/abd/pelvis). Monitor for interstitial lung disease via pulmonary function tests and high-resolution CT.
Differential Diagnosis
Polymyositis: lacks pathognomonic skin findings
Inclusion body myositis: distal muscle involvement and older males
Systemic lupus erythematosus: malar rash spares nasolabial folds
Drug-induced myopathy: history of statin use
Hypothyroidism: associated with elevated TSH