[Arrector pili myositis in a patient with dermatomyositis: an unusual histological feature]

Dermatomyositis is a rare inflammatory disease with a difficult diagnosis on cutaneous biopsies, since alterations are often little marked and non specific. A 52-year-old patient had severe paraneoplastic dermatomyositis. He had an erythematous rash on the trunk, and erythematous papules on the back of the hands. The first histological cutaneous lesion was a striking arrector pili myositis. Arrector pili myositis has rarely been described, and is thought to be linked with Wong type eruption occurring in dermatomyositis. Arrector pili myositis might constitute an helpful sign in the diagnosis of dermatomyositis, but its specificity and sensitivity are unknown. We compared this case to four previously reported cases. In these five cases, arrector pili myositis was not associated with a particular sub-type of dermatomyositis or with poor prognosis.