Isolated autosomal recessive woolly hair/hypotrichosis: genetics, pathogenesis and therapies. Isolated 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. Woollyhairautosomalrecessive 1 (ARWH1) (MIM #278150), woollyhairautosomalrecessive 2 (ARWH2) (MIM #604379) and woollyhairautosomalrecessive 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