Amyopathic dermatomyositis in children: a diagnostic and therapeutic dilemma.

Juvenile dermatomyositis is an inflammatory disease of unknown etiology that primarily affects skin and muscles. The pathognomonic Gottron's sign consists of symmetric macules and papules on the dorsal aspect of the interphalangeal joints and exterior areas of the big joints. A periorbital violaceous (heliotrope) skin rash is also characteristic. There may be a discordance in time of presentation of the skin and muscle disease, and a small subset of patients apparently do not develop muscle disease at all. The absence of muscle involvement is termed 'amyopathic dermatomyositis.'We describe two children who presented with the characteristic rash of juvenile dermatomyositis but with no clinical evidence of muscle involvement. One developed muscle weakness 3 years later. Neither patient had a full muscle work-up at the onset of the disease, which left questions about diagnoses and whether or not there may have been subtle muscle involvement. On the basis of our literature review, the outcome of these patients is uncertain, although it appears that myositis develops in many, maybe most, affected children. We suggest that in the absence of muscle disease, application of sunscreen and administration of hydroxychloroquine sulfate may ameliorate the rash. More aggressive treatment will need to be given when muscle involvement can be demonstrated.