SASH1 Mutations and Hereditary Disorders of Pigmentation: Review of Literature.

Dyschromatosis universalis hereditaria (DUH) is a rare genodermatosis characterized by asymptomatic hyper- and hypopigmented macules appearing in infancy and persisting for life. Although mutations in ABCB6 account for many DUH cases, recently, the SAM and SH3 domain-containing 1 (SASH1) gene has emerged as a key player in DUH. Additionally, SASH1 mutations have been associated with the pure-lentiginous phenotype of familial pigmentation. In this review of literature, we found 22 different SASH1 mutations, most inherited in an autosomal dominant manner. These variants cause distinct phenotypes, including DUH, lentiginosis, and rarely, an autosomal recessive syndromic form with alopecia, palmoplantar keratoderma, and increased risk of malignancies. Functional studies have revealed that SASH1 acts as both a tumor suppressor and a pro-melanogenic factor. It modulates key pathways such as p53-POMC-α-MSH-MC1R-MITF and Gαs-SASH1-IQGAP1-E-cadherin pathways, affecting melanosome production, transport, and melanocyte migration. This unique dual role of SASH1 highlights its importance in melanocyte homeostasis and UV-induced pigmentation. Understanding the role of SASH1 in regulating pigmentation can help foster novel therapeutic approaches for these genodermatoses and related pigmentary anomalies, ultimately improving patient care and outcomes.