Cutaneous macroglobulinosis is a rare skin manifestation of Waldenstrom macroglobulinemia. It is characterized by the deposition of eosinophilic, immunoglobulin-derived material in the dermis. It typically presents as pink or skin-colored papules favoring the extensor surfaces of the extremities. There are 11 reported cases of cutaneous macroglobulinosis in the literature. In our consultative dermatopathology practice we encountered three additional cases. In Case 1, a 41-year-old female with a monoclonal immunoglobulin M (IgM)-kappa gammopathy developed skin-colored papules on her extensor extremities, forehead and back. Histopathologic and immunohistochemical analyses revealed periodic acid-Schiff (PAS)-positive pink material in the dermis that stained with IgM. In Case 2, an 83-year-old female with a monoclonal IgM-lambda paraproteinemia developed non-blanching papules and plaques on the lower extremities and cheeks. Skin biopsies showed a striking occlusion of the vessels with a PAS-positive eosinophilic precipitate, which was also found in the extravascular spaces and stained with IgM using direct immunofluorescence (DIF) and immunohistochemical stains. In Case 3, an 80-year-old male with Waldenstrom macroglobulinemia developed ulcerated papules and nodules on the lower extremities. The biopsy findings were similar to those of Case 2. We present a series of three patients with cutaneous macroglobulinosis and explore variations in the clinical and histopathological findings of this uncommon entity.
