AbstractIsolated autosomal recessive woolly hair/hypotrichosis (ARWH) is a rare hereditary hair disease characterized by tightly curled sparse hair at birth or in early infancy. Patients with ARWH consist of genetically heterogeneous groups. Woolly hair autosomal recessive 1 (ARWH1) (MIM #278150), woolly hair autosomal recessive 2 (ARWH2) (MIM #604379) and woolly hair autosomal recessive 3 (ARWH3) (MIM #616760) are caused by mutations in LPAR6, LIPH and KRT25, respectively. In addition, nonsense variants in C3ORF52 (*611956) were identified in ARWH patients. The frequencies of the mutations in the causative genes in ARWH patients are thought to differ by ethnicity and country/geographical area. Large numbers of ARWH families with LIPH mutations have been described only in populations from Japan, Pakistan and the Volga–Ural region of Russia. In that region of Russia, most ARWH families have an extremely prevalent founder mutation, the deletion of exon 4, in LIPH. In the Pakistani population, 47.2% of ARWH families had the disease due to LIPH mutations and 52.8% of them carried LPAR6 mutations. The prevalent, recurrent LIPH mutation c.659_660delTA (p.Ile220Argfs*29) was found in more than half of Pakistani ARWH families with LIPH mutations. Most Japanese ARWH families (98.7%) harbour LIPH mutations, including the two highly prevalent, recurrent LIPH mutations c.736T>A (p.Cys246Ser) and c.742C>A (p.His248Asn). In ARWH patients whose disease was due to LIPH, LPAR6 or C3ORF52 mutations, the loss of function of LIPH, LPAR6 or C3ORF52 leads to reduced LIPH‐LPA‐LPAR6 signalling, resulting in the decreased transactivation of EGFR signalling and the phenotype of underdeveloped hairs. Our recent prospective interventional study suggests that topical minoxidil might be a promising treatment for ARWH due to LIPH mutations, although sufficiently effective treatments have not been established for ARWH yet.