Cutaneous and systemic plasmacytosis showing histopathologic features as mixed-type Castleman disease: a case report

Cutaneous and systemic plasmacytosis (CSP) is a rare disorder characterized by disseminated reddish brown plaques and polyclonal hypergammaglobulinemia. The lesions of CSP are histologically characterized by an infiltration of mature polyclonal plasma cells, which display similar pathological features to the plasma cell-type Castleman disease (CD). The relationship between CSP and CD is controversial. Herein, we described a 43-year-old man from China with disseminated reddish brown plaques and nodules on the cheek and temple. The serum level of immunoglobulin G and immunoglobulin A were higher than normal. In addition to mature plasma cell perivascular infiltrate in the dermis, the biopsy of the lesions showed small to medium-sized germinal follicles with hyalinized vessels and a concentrically arranged mantle zone. The patient had clinical features of CSP, but the biopsy revealed changes resembling mixed-type CD. To the best of our knowledge, this is the first case of CSP with the pathological features of mixed-type CD reported from China.