Monilethrix: A Novel Mutation (Glu402Lys) in the Helix Termination Motif and the First Causative Mutation (Asn114Asp) in the Helix Initiation Motif of the Type II Hair Keratin hHb6

The study identified novel mutations associated with monilethrix, a rare hair disorder, in the type II hair keratin hHb6. A new Glu402Lys mutation in the helix termination motif (HTM) was found in an American family, indicating a spontaneous germ-line mutation. Additionally, a critical Asn114Asp mutation in the helix initiation motif (HIM) was discovered in a Swedish family, linked to severe disease phenotypes such as complete baldness and follicular keratosis. These findings suggested that monilethrix is a disease of the hair cortex, with mutations primarily occurring in type II hair keratins, particularly in the HTM and HIM regions. The study emphasized the role of specific point mutations in keratin genes in causing hereditary hair disorders.