The amyloid–melanin connection: a cross sectional study on primary cutaneous Macular Amyloidosis

Abstract

Context: Amyloidosis is group of rare diseases that are characterized by extracellular deposition of abnormal amyloid proteins either involving multiple organ systems (systemic amyloidosis) or restricted to a single-tissue site, such as skin (localized amyloidosis). In primary cutaneous amyloidosis, there is deposition of amyloid in apparently normal skin. The hyperpigmentation in all the lesions of primary cutaneous macular amyloidosis gives us an insight of a possibility of a connection between amyloid fibrils and melanogenesis. Aims: To compare the melanin content from the lesional skin of upper back and surrounding non-lesional skin of macular amyloidosis. Settings and Design: A hospital based, cross-sectional study conducted over a period of 6 months. Methods and Materials: Forty-two patients (30 females and 12 males) clinically and histopathologically diagnosed as macular amyloidosis were enrolled in the study. A Mexameter MX18 was used to measure the melanin index of the lesions of Macular amyloidosis over upper back and non-affected similar areas (control). Results: The melanin index of the lesional skin of female patients ranged from 552 to 823 (mean\u2009=\u2009705.1). The melanin index of the lesional skin of male patients ranged from 621 to 792 (mean\u2009=\u2009697.41). In the non-affected surrounding skin of females, the mean melanin index was 357.66, whereas in males, the melanin index of the surrounding normal skin was 296.75. The P value came out to be significant, that is, <0.05 in both males and females. Conclusions: There is a possible connection between amyloid fibrils and melanin synthesis. Amyloid protein in primary macular cutaneous amyloidosis may act as the precursors for melanogenesis.