Primary cutaneous amyloidosis

Primary cutaneous amyloidosis (PCA) is a group of skin disorders characterized by the abnormal deposition of amyloid protein exclusively in the skin, without involvement of internal organs. The three main clinical subtypes are macular amyloidosis, lichen amyloidosis, and nodular amyloidosis (also called primary localized cutaneous amyloidosis). Macular amyloidosis presents as itchy, rippled, brownish patches typically on the upper back and extremities. Lichen amyloidosis manifests as intensely pruritic, firm, raised papules most commonly on the shins. Nodular amyloidosis presents as waxy nodules or plaques, usually on the limbs, face, or trunk. The condition primarily affects the integumentary system (skin), and chronic pruritus (itching) is a hallmark feature, particularly in the macular and lichen forms. The amyloid deposited in macular and lichen forms is derived from keratin (keratinocyte-derived amyloid), while nodular amyloidosis involves immunoglobulin light chain-derived amyloid produced by local plasma cells. Primary cutaneous amyloidosis is more prevalent in certain populations, particularly in Southeast Asia, South America, and the Middle East. Familial forms have been described, some of which are associated with mutations in the OSMR gene (encoding oncostatin M receptor) or the IL31RA gene, both linked to familial primary localized cutaneous amyloidosis. These familial cases typically follow an autosomal dominant inheritance pattern. However, most cases are sporadic. Nodular amyloidosis carries a small risk (approximately 7-50% in some series) of progression to systemic AL amyloidosis, so long-term monitoring is recommended for this subtype. Treatment is primarily symptomatic and aimed at relieving pruritus and improving cosmetic appearance. Options include topical corticosteroids, topical calcineurin inhibitors, antihistamines, phototherapy (UVB or PUVA), and dimethyl sulfoxide (DMSO). For lichen amyloidosis, treatments such as laser therapy and dermabrasion have been used with variable success. Nodular amyloidosis may be managed with surgical excision or laser ablation. There is currently no curative therapy, and recurrence after treatment is common. Patients with nodular amyloidosis should undergo periodic evaluation to exclude progression to systemic amyloidosis.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about Primary cutaneous amyloidosis