Unusual cutaneous involvement during plasma cell leukaemia phase in a multiple myeloma patient after treatment with thalidomide: a case report and review of the literature

Summary We report the case of a 54‐year‐old African–American male with IgG multiple myeloma (MM) with disease resistant to multiple chemotherapy regimens and immunomodulatory treatment with thalidomide. In spite of achieving a partial remission of short duration, his disease accelerated to peripheral plasmacytosis and subsequent development of cutaneous plasmacytomas. The malignant plasma cells derived from the dermal lesions were CD45+, CD38+, CD138+ and matched the immunophenotype of the plasmacytes during the leukaemic phase. Occurrence of extramedullary lesions in the setting of MM treated with thalidomide is of concern, although currently there are very few reports describing this association. We discuss the possible relationship between the patient's unusual disease course and the administered chemo‐ and immunotherapy. The significance of the changes in adhesion molecules, especially CD 138 and CD 56, relevant to the development of cutaneous plasmacytomas is discussed.