Genetics of Alopecia

Abstract

Abstract A recent genome‐wide association study showed eight regions for alopecia areata (AA), including CTLA4 , IL‐2/IL‐22 , HLA‐class II , UL16‐binding protein‐3 and ‐6 , syntaxin 17 , IL‐2RA , peroxiredoxin 5 and Eos . Candidate genes associated with androgenetic alopecia are divided into androgen‐related and ‐unrelated genes. The former includes 5 α‐ reductase isozymes , androgen receptor and ectodysplasin A2 receptor , which is located close to androgen receptor (AR) gene, and possible AR coregulator such as histone deacetylase 9 . The latter contains PAX1 and FOXA2 . Regarding congenital hypotrichosis, mutations in EDA‐A1 , EDAR and EDA‐RADD , p63 and P‐cadherin are pointed out for ectodermal dysplasia, SPINK5 for Netherton syndrome, desmoglein 4, lipase H (LIPH) and LPAR6 (P2RY5) for localised autosomal recessive hypotrichosis, lipase H (LIPH) and LPAR6 (P2RY5) for autosomal recessive woolly hair, keratin 74 for autosomal dominant woolly hair, corneodesmosin and APCDD for hypotrichosis simplex and hairless for Marie‐Unna hypotrichosis. Key Concepts: Recent studies using mainly genome‐wide association analysis revealed novel candidate genes associated with alopecia, providing informative explanation for the pathogenesis. Genome‐wide association studies suggested the importance of innate and acquired immunity in alopecia areata pathogenesis and possibility of androgen‐independent pathogenic pathway in androgenetic alopecia. Novel genes associated with congenital hypotrichosis have been found, providing new clues to search not only the pathogenesis but also molecular mechanism of normal hair growth.