Case report: Clinicopathological characteristics of SASH1 mutation-related dyschromatosis: a rethinking of the classification of dyschromatosis

Dyschromatosis, a group of pigmentary dermatoses, accompany both hyper- and hypo-pigmentation, including dyschromatosis symmetrica hereditaria (DSH), dyschromatosis universalis hereditaria (DUH), and familial progressive hyper- and hypo-pigmentation (FPHH). A peculiar phenotype of dyschromatosis presented as multiple lentigines and hypopigmentation with various sizes and shapes was found to be associated with <i>SASH1</i> mutations and has recently been reported frequently. The current study evaluated the clinical manifestation, pathological pattern, and genetic basis of dyschromatosis in a five-generation family. This research also presents a case study of a sporadic patient with dyschromatosis caused by <i>SASH1</i> mutations and shows different clinicopathological characteristics form DSH, DUH and FPHH. SASH1 (SAM and SH3 Domain Containing 1) gene, located on chromosome 6q24.3, encodes a tumor suppressor protein involved in cell signaling, migration, and adhesion. Additionally, the <i>SASH1</i> mutations could also lead to another pigmentary phenotype: multiple lentigines. High consistency in clinicopathological features and genetic basis in these two <i>SASH1</i>-related pigmentary disorders suggests that <i>SASH1</i> mutations cause multiple lentigines and dyschromatosis which might belong to a disease spectrum. Overall, it is expected the current study results could help enhance a more comprehensive understanding of <i>SASH1</i>-related pigmentary dermatoses.