Dermatomyositis

This patient is exhibiting pathognomonic cutaneous findings of dermatomyositis which are the heliotrope rash and Gottron's papules. The heliotrope rash consists of a dark lilac discoloration or a violaceous to dusky erythematous rash with or without edema in a symmetrical distribution involving periorbital skin. Often only the upper lid is involved. This rash may follow the course of myositis or it may wax/wane discordantly with the disease activity. Gottron's papules are found over the bony prominences, particularly over the metacarpophalangeal joints, the proximal interphalangeal joints or distal interphalangeal joints. Occasionally, they are found over bony prominences like the elbow, knee and feet. They are violaceous papules and plaques often with telangiectasia within the lesion.

Clinically, the myopathy affects mainly proximal muscle groups of the shoulder and pelvic girdle. In severe progressive disease, all muscles may become involved. The disease is usually symmetrical. Muscle ache is a common complaint, but frank tenderness on palpation is variable. Dysphagia (involvement of the striated muscles of the pharynx or upper esophagus) often signifies a rapidly progressive course is estimated to occur in 15-50% of patients.

Enzymes commonly elevated include creatine kinase, aldolase, lactic dehydrogenase and/or serum transaminases.

Arthralgias and/or arthritis may be present in upto 25% of patients. Usually, this is generalized and accompanied by morning stiffness.

Pulmonary disease occurs in 15-30% of patients and is characterized as a primary diffuse interstial fibrosis. Lung disease may also occur as a direct complication of the muscle disease, i.e. hypoventilation or aspiration.

Keep in mind that the most frequently identified antibody, anti-Jo-1, is found in only 20% of all myositis patients tested (2). Anti-Jo-1 is the most common of a group of anticytoplasmic aminoacyl-tRNA synthetase enzymes and is itself directed against histidyl-tRNA synthetase.

Another physical finding in dermatomyositis is the "machinist hands" with cracking and fissuring of the distal digital skin of the fingerpads.

Reference:

  1. Callen JP. Dermatomyositis: an update on diagnosis, evaluation and management. Resident & Staff Physician; Feb 1995:21-28.
  2. Arnett FC, Hrsch TJ, Bias WB, Nishekai M, Reichlin M. The Jo-1 antibody system in myositis: Relationships to clinical features and HLA. J. Rheumatol. 1981; 8: 925-30.

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