Abstract
Cutaneous manifestations of monoclonal gammopathy can precede, be concurrent with, or follow the onset of the plasma cell disorder. These manifestations may be classified as specific, resulting from direct infiltration of the skin by malignant plasma cells, or nonspecific. The specific skin lesions include extramedullary plasmocytoma and secondary cutaneous involvement by direct extension from underlying bone neoplasms. The nonspecific manifestations include cutaneous changes that occur as a result of indirect effects of the abnormal immunoglobulins, such as their deposition in the skin (amyloidosis in multiple myeloma and storage papules of Waldenstrom’s macroglobulinemia) or in the lumen of the vessels (cryoglobulinemia), the biologic activity of abnormal proteins (necrobiotic xanthogranuloma and diffuse-plane normolipemic xanthoma) and abnormal cytokine secretion (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin changes [POEMS] syndrome). In some cases, the pathogenetic mechanism that links monoclonal gammopathy and the cutaneous disorders remains elusive.