Hypotrichosis simplex refers to a group of hereditary isolated alopecias characterized by diffuse and progressive hair loss, usually beginning in early childhood. Localized autosomal recessive hypotrichosis (LAH) is characterized by fragile hairs that break easily, leaving short, sparse scalp hairs. The disorder affects the trunk and extremities as well as the scalp, and the eyebrows and eyelashes may also be involved, whereas beard, pubic, and axillary hairs are largely spared. In addition, patients can develop hyperkeratotic follicular papules, erythema, and pruritus in affected areas. Woolly hair (WH) refers to a group of hair shaft disorders that are characterized by fine and tightly curled hair. Compared to normal curly hair that is observed in some populations, WH grows slowly and stops growing after a few inches. Under light microscopy, WH shows some structural anomalies, including trichorrhexis nodosa and tapered ends. [From OMIM]