Nodular cutaneous amyloidosis

Nodular cutaneous amyloidosis (also known as nodular amyloidosis of the skin or tumefactive cutaneous amyloidosis) is a rare, localized form of amyloidosis in which abnormal amyloid protein deposits accumulate in the skin, forming nodular lesions. Unlike systemic amyloidosis, the amyloid deposits in this condition are primarily confined to the skin and subcutaneous tissue. The amyloid deposited is typically composed of immunoglobulin light chains (AL type), produced by a local clonal proliferation of plasma cells within the skin. It is classified among the primary localized cutaneous amyloidoses, which also include macular and lichen amyloidosis, but nodular cutaneous amyloidosis is distinct in its clinical presentation and underlying pathology. Patients typically present with one or more waxy, firm, smooth nodules or plaques on the skin, which may be skin-colored, pink, or brownish. The lesions most commonly appear on the legs, trunk, face, or genitalia. They are usually painless but may occasionally be pruritic or tender. The nodules can vary in size from a few millimeters to several centimeters. Although the condition is generally benign and localized, an important clinical concern is that a small proportion of patients (estimated at 7–50% depending on the series) may progress to systemic AL amyloidosis over time. Therefore, long-term follow-up with periodic screening for systemic involvement — including serum and urine protein electrophoresis, free light chain assays, and organ function assessments — is recommended. There is no universally established curative treatment for nodular cutaneous amyloidosis. Management options include surgical excision, laser therapy (such as carbon dioxide laser), and observation with monitoring. Recurrence after excision is common. In cases where systemic progression is detected, treatment follows protocols for systemic AL amyloidosis, which may include chemotherapy or other targeted therapies. Given the risk of systemic progression, a multidisciplinary approach involving dermatology, hematology, and clinical genetics is advisable for long-term management.

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