Primary cutaneous nodular amyloidosis associated with psoriasis

Primary cutaneous nodular amyloidosis (PCNA) presents as solitary or multiple firm, waxy nodules with a predilection for acral areas. Histologically, PCNA can be identical to myeloma‐associated systemic amyloidosis with monoclonal immunoglobulin light chain deposits. We describe a patient in whom PCNA developed in a scar in an area affected by chronic plaque psoriasis. PCNA has previously been associated with other autoimmune diseases, but to our knowledge, this is the first association with psoriasis. Interestingly, T helper (Th)17 cells, which are crucial in psoriasis pathogenesis, have recently been implicated in promotion of myeloma and plasma cell dyscrasias. The association of psoriasis and plasma‐cell light chain production in the skin, as in this case, suggests a possible role for Th17 cells in PCNA formation. The dermatopathological literature of this rare but important disease is discussed.