Pathogenesis of Paraneoplastic Follicular Hyperkeratotic Spicules in Multiple Myeloma

• We describe a 62-year-old man with multiple myeloma who developed horny spicules on his face, particularly on his nose. IgG-λ monoclonal gammopathy was detected, and the serum dysprotein was shown to be a cryoglobulin, which forms a cryogel at low temperatures. Light and electron microscopic and immunohistochemical examinations showed an intercellular precipitation and massive accumulation of the IgG dysprotein and cryoglobulin between the keratinocytes of the upper epidermis and the infundibular epithelium. The follicles were dilated and filled with parakeratotic cells, the protein deposits between them and a rudimentary hair thus resulting in the clinically visible symptoms of horny spi…