Fever, Pancytopenia, and Tender Erythematous Plaques in a Patient With Multiple Myeloma

A man in his late 60s was referred to the dermatologic clinic with a 10-day history of fever up to 38.5 °C and tender lesions on the neck and trunk. In the previous month, he had received the first cycle of a chemotherapeutic regimen of ixazomib, lenalidomide, and dexamethasone to treat a recurrence of IgG-κ multiple myeloma with a 10-year history. Physical examination showed annular erythematous plaques of up to 2 cm in diameter, with violaceous and crusted centers on the neck and trunk. On the right chest, an annular erythematous lesion with 2 zones of color—a central area of purpura and an outer erythematous and edematous ring—was present (Figure, A). Laboratory investigations found pancytopenia: a white blood cell count of 2.3 × 10³/μL (reference range, 3.5-9.8 × 10³/μL), hemoglobin levels of 12.1 g/dL (reference range, 13.5-17.6 g/dL), platelet count of 29 × 10³/μL (reference range, 130-400 × 10³μL), and elevated serum C-reactive protein levels of 3.31 mg/dL (reference range, <0.30 mg/dL). Blood culture results were negative. Granulocyte colony-stimulating factor analogs had not been prescribed to the patient. Skin biopsy from a lesion on the left chest was performed for histopathological and immunohistochemical analyses (Figure, B-D).