Monilethrix: A Keratin HHb6 Mutation Is Co-Dominant With Variable Expression

Monilethrix was identified as a rare autosomal dominant condition marked by hair fragility and hyperkeratotic papules, linked to mutations in type-II hair-specific keratins hHb6 and hHb1. The study described a large family with an E410D mutation in the keratin hHb6 gene, showing variable expression among 12 heterozygous members and severe expression in 3 homozygous members. These 3 individuals experienced almost complete scalp hair loss from 2 months of age, with no improvement over time, and extensive follicular keratotic involvement. The variability in expression among heterozygous patients, along with observed seasonal and pregnancy-related improvements, suggested that other genetic or environmental factors might influence keratin gene expression. This was the first report of a co-dominant keratin hHb6 mutation leading to severe disease.