Reddish-brown, papulonodular skin lesions in the periungual region

Multicentric reticulohistiocytosis is a rare, non-Langerhans cell histiocytosis that most commonly presents in women in their fourth or fifth decades of life. Cutaneous involvement, characterized by reddish-brown papules in a "string of pearls" or "coral bead" linear formation, and joint involvement are the two most common manifestations at presentation. Histopathology demonstrates dermal proliferation of epithelioid histiocytic-appearing cells with ground glass cytoplasm. We report a 51-year-old woman who presented with ruddy, periungual papules and bilateral joint pain in the hands, consistent with multicentric reticulohistiocytosis. We describe the clinical and histopathologic presentation, therapeutic options, and differential diagnosis of this rare condition.