Multicentric reticulohistiocytosis with dermatomyositis-like features: a more common disease presentation than previously thought.

Multicentric reticulohistiocytosis (MRH) is a rare form of non-Langerhans histiocytosis that presents with erosive arthritis and skin nodules. Approximately 25% of patients with MRH have an associated malignancy. Dermatomyositis is an inflammatory autoimmune condition that has also been associated with malignancy. To date, 7 cases of MRH have been reported to present with cutaneous features of dermatomyositis. We describe an eighth patient with MRH who presented with dermatomyositis-like features (V-neck erythema, shawl sign, Gottron's papules and periungual erythema), who developed metastatic breast cancer 1 year after diagnosis. We hypothesized that clinical overlap between MRH and dermatomyositis was not as uncommon as review of the literature suggested. Careful review of the physical exam findings and photographs of the 234 papers reporting MRH revealed 27 cases of MRH with dermatomyositis-like features. Of these 27 cases, 7 (26%) were associated with a malignancy. Skin biopsies of the cutaneous features mimicking dermatomyositis revealed pathologic features of MRH. This is a descriptive analysis of published case reports. Based on a review of published case reports, MRH presenting with dermatomyositis-like features is likely fairly common. Histological examination of skin biopsies allows for disease differentiation. Differentiating MRH from dermatomyositis is important for management decisions and comorbidity screening.