Amyloid and amyloidosis.

Cutaneous lesions are present in up to 40% of patients with primary and myeloma-associated systemic amyloidosis and occur as a result of tissue deposition of immunoglobulin light chain material derived from a circulating paraprotein. The occurrence of waxy, purpuric mucocutaneous lesions provides a crucial early pointer to underlying occult plasma cell dyscrasia; the combination of the symptoms of the carpal tunnel syndrome, macroglossia, and specific mucocutaneous lesions is highly characteristic. Although secondary systemic (reactive) amyloidosis rarely gives rise to clinically evident cutaneous lesions, it may be etiologically related to a number of chronic dermatoses. Lesions of nodular primary localized cutaneous amyloidosis are indistinguishable from those of primary and myeloma-associated systemic amyloidosis, and they result from local plasma cell infiltration. Macular and papular (lichen amyloidosus) variants of primary localized cutaneous amyloidosis may have a familial or racial basis and are characterized by a tendency for keratinocytes to undergo filamentous degeneration and apoptosis. The prognosis of patients with plasma cell dyscrasia-related systemic amyloidosis remains poor, since there is little response to therapy with cytotoxic agents, colchicine, or dimethylsulfoxide. Colchicine is the drug of choice in the prevention and treatment of the renal amyloidosis associated with familial Mediterranean fever, and dimethylsulfoxide may be useful in the management of patients with secondary systemic amyloidosis. Macular amyloid and lichen amyloidosus generally follow a chronic course with intractable pruritus; there have been isolated reports of the beneficial effect of dermabrasion, topical dimethylsulfoxide, and therapy with the aromatic retinoid, etretinate.