Primary localized cutaneous amyloidosis − a review

Amyloidosis describes a group of diseases characterized by abnormal extracellular deposition of a fibrillar protein in tissues. It comprises of a spectrum of diseases ranging from a mild asymptomatic cutaneous involvement to a progressive life-threatening multisystem disorder. Primary localized cutaneous amyloidosis (PLCA) is characterized by pruritus, hyperpigmentation, and lichenification. Demonstration of amyloid in dermal papillae by various techniques confirms the diagnosis. Three types are described, macular, lichen/papular, and nodular. Majority of cases of PLCA are sporadic but an autosomal dominant family history may be present in up to 10% of cases. Exact pathogenesis is not elucidated yet, but several factors like friction, sunlight, genetics, atopy, immune dysregulation have been implicated. Pathogenic mutations in oncostatin M receptor and the interleukin (IL)-31 receptor A gene (IL31RA) have an important role to play in the pathogenesis of both familial and sporadic PLCA. Nodular amyloidosis, the rarest type of PLCA, is known to progress to systemic amyloidosis in 7% to 15% of cases, hence a long-term follow up is recommended. The plethora of treatment options reported to be beneficial in cutaneous amyloidosis underscores the fact that none of the modality is universally effective.