Cutaneous Plasmacytosis: A Rare Encounter

Abstract

Background: Cutaneous plasmacytosis (CP) is a rare skin condition characterized by the presence of multiple reddish-brown nodules resulting from polyclonal plasma cell proliferation. While it is most commonly reported on the trunk, it can also affect the face and extremities in adults, with a higher prevalence in Asian populations. The underlying cause of CP remains unclear, and there is no established consensus on effective treatment approaches. Case report: A 58-year-old man with a background of renal failure on hemodialysis seeks advice regarding persistent asymptomatic papules and plaques on the back, neck and trunk which gradually increased over three years. Physical examination revealed multiple discrete infiltrative erythematous to brownish plaques and nodules on the face, neck, trunk and back, with some pustules in certain areas. The skin biopsy showed mature plasmacytic dermal infiltrate requiring immunohistochemical study. The immunohistochemistry showed no light chain restriction, confirming the polyclonal nature of the plasma cells, which supports the diagnosis of plasmacytosis the novelty of the article lies in the first published case of African descent. Discussion: Cutaneous plasmacytosis is a rare condition of uncertain origin, often indicating a slow-developing systemic disorder. It predominantly affects middle-aged men of Japanese ancestry. The typical manifestations include multiple red-brown papules and plaques with minimal changes to the epidermis. Diagnosis relies on histopathological examination, revealing dense perivascular infiltrates of mature polyclonal plasma cells without atypia. Systemic involvement, termed systemic plasmacytosis, is characterized by cutaneous lesions alongside lymphadenopathy and polyclonal hypergammaglobulinemia. Treatment strategies for cutaneous plasmacytosis remain scarce, lacking a standardized approach.