Be alert for dermatomyositis without muscle disease
LAS VEGAS – Dermatologists need to be alert for amyotrophic dermatomyositis in patients with rash where lupus might be considered, because of the need for vigilant surveillance for cancer and lung disease in this population.
Ruth Ann Vleugels, MD, walked attendees through a series of dermatomyositis diagnostic pearls at the annual Perspectives in Rheumatic Diseases held by Global Academy for Medical Education.
“When a patient has dermatomyositis but doesn’t have muscle disease, you really have to rely on the skin findings,” since you’re lacking the tipoff of muscle disease at presentation, Dr. Vleugels, professor of dermatology at Brigham and Women’s Hospital, Boston, said in an interview. This is especially true because, on biopsy, “the pathological findings are identical to that of lupus,” she said.
Dr. Vleugels emphasized that it’s important not to miss a more subtle, less violaceous heliotrope eruption, especially in lighter-skinned patients; similarly, Gottron’s papules are not always papular and limited to the knuckle pads, but can be more macular and linear, with psoriasiform scaling. Nail findings such as dilated capillary loops with dystrophic and hypertrophied cuticles are also a big clue. Photodistributed erythema – the “shawl sign” – can be subtle, but offers additional support for a dermatomyositis diagnosis.
Though the erythematous midface rash of lupus resembles a dermatomyositis rash in many ways, there’s a critical differentiator of the two rashes, Dr. Vleugels said. “In dermatomyositis patients, it very classically hugs, or involves, the nasolabial folds, whereas in our systemic lupus patients, the erythema of the cheeks spares the nasolabial folds.”
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