Mapping of Monilethrix to the Type II Keratin Gene Cluster at Chromosome 12q13 in Three New Families, Including One with Variable Expressivity

The study investigated monilethrix, an autosomal dominant disorder affecting hair, in three new families from England, Scotland, and Spain. The research confirmed linkage to the type II keratin gene cluster at chromosome 12q13, with a significant Zmax of 6.34, and excluded linkage to the type I keratin gene cluster on 17q. One family exhibited a variant phenotype with only follicular keratosis and no hair anomalies, highlighting variable expressivity and non-penetrance. The findings supported the hypothesis that monilethrix was a disorder of hard keratins, though no evidence linked it to defects in type I keratins.