Clinical Pearls & Morning Reports
Published December 8, 2021
The classic categories of idiopathic inflammatory myopathy are inclusion-body myositis, polymyositis, overlap syndromes (e.g., Sjögren’s syndrome and lupus), necrotizing myositis (e.g., statin-induced myositis), antisynthetase syndrome, and dermatomyositis. Read the NEJM Case Records of the Massachusetts General Hospital here.
Q: What are the two most common rheumatic diseases associated with anti-Ro antibodies?
A: The most common rheumatic diseases associated with anti-Ro antibodies are Sjögren’s syndrome and systemic lupus erythematosus. Less common diseases associated with anti-Ro antibodies are inflammatory myositis, mixed connective-tissue disease, and primary biliary cholangitis.
Q: Describe the typical cutaneous manifestation of dermatomyositis.
A: Typical cutaneous manifestations of this disease include Gottron’s papules (erythematous papules on the metacarpophalangeal and proximal interphalangeal joints and other extensor surfaces), heliotrope rash (an erythematous-to-purplish rash that often involves the eyelids and surrounding area), V sign (also known as shawl sign, an erythematous rash on the front and back of the torso), and holster sign (an erythematous rash that involves the lateral hip area).
A: In one approach to the evaluation of a patient with myositis, the first step is to characterize the distribution of muscle involvement as symmetric or asymmetric. Pyomyositis and diabetic muscle infarction tend to have an asymmetric distribution, whereas rheumatic diseases tend to be associated with symmetric myositis. The exception is inclusion-body myositis, which tends to be asymmetric. In patients with symmetric myositis, the next step in the evaluation is to characterize the distribution as primarily proximal or distal. With rheumatic diseases, except for inclusion-body myositis, proximal rather than distal muscles tend to be involved. Endocrinopathies, such as hypothyroidism, can also cause symmetric proximal myopathy.
A: Anti–MDA-5 antibodies are associated with dermatomyositis with unique cutaneous features, especially skin ulcerations and nodular lesions, along with rapidly progressive interstitial lung disease and subtle myopathy; indeed, many cases of anti–MDA-5 dermatomyositis are amyopathic. Cutaneous ulcerations overlying the metacarpophalangeal and interphalangeal joints, elbows, and nail folds are seen in up to 85% of patients with anti–MDA-5 dermatomyositis, often with lateral digital hyperkeratosis. Approximately 50% of cases are associated with oral ulcers, often on the tongue. Arthralgias, fever, presence of anti-Ro antibodies, abnormal results on liver-function tests, and elevated ferritin level are common in patients with anti–MDA-5 dermatomyositis.