Macular amyloidosis

Macular amyloidosis is a form of primary localized cutaneous amyloidosis (PLCA) characterized by the deposition of amyloid protein in the skin, specifically in the papillary dermis. It is one of the most common subtypes of cutaneous amyloidosis and primarily affects the skin without involvement of internal organs. The condition presents as itchy (pruritic), brownish or grayish-brown, rippled or reticulated (net-like) hyperpigmented macules, most commonly found on the upper back, particularly the interscapular region, though it can also appear on the arms, chest, and other areas. The amyloid deposits in macular amyloidosis are derived from degenerated keratin filaments of epidermal keratinocytes (known as amyloid K). The condition is more prevalent in certain ethnic groups, particularly individuals of Asian, South American, and Middle Eastern descent, and tends to affect women more frequently than men. The exact cause of macular amyloidosis is not fully understood, but it is thought to involve chronic friction or scratching of the skin (such as from towel rubbing or use of nylon brushes), which leads to keratinocyte damage and subsequent amyloid deposition. Some familial cases have been reported, suggesting a possible genetic predisposition, and associations with mutations in the OSMR gene (encoding oncostatin M receptor) and IL31RA gene have been identified in familial forms of PLCA. The condition is generally benign and does not progress to systemic amyloidosis, but the persistent pruritus and cosmetic changes can significantly affect quality of life. Treatment of macular amyloidosis is primarily symptomatic and aimed at relieving itching and improving the appearance of affected skin. Topical corticosteroids, calcineurin inhibitors (such as tacrolimus), and antihistamines may help manage pruritus. Phototherapy (narrowband UVB or PUVA) has shown some benefit in reducing pigmentation and itching. Other reported treatments include topical dimethyl sulfoxide (DMSO), dermabrasion, and laser therapy, though results are variable. Avoidance of chronic friction to the affected areas is recommended as a preventive measure. There is currently no cure for the condition, and recurrence after treatment is common.

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

Common questions about Macular amyloidosis