Abstract: Objective To investigate the gene mutation in a pedigree with monilethrix and the correlation between the genotype and phenotype of monilethrix.Methods Light microscopy was used to observe the structure of hair shafts;PCR and direct DNA sequencing were employed to determine the mutation sites and modes.Results The hair shafts showed a regular periodicity of nodes and narrow intemodes,like a pearl necklace.A heterozygous transition mutation of G→A at position 1204 in exon 7 ofhHb6 gene was determined in the affected relatives of the pedigree,but not found in his healthy relatives or 50 unrelated individuals.Conclusions The E402K mutation of hHb6 gene may be pathogenic for this case of monilethrix.The gene mutation,likely with other cofactors,may cause the phenotypic variation of monilethrix.

Key words: Hair diseases, Keratin, Genes, Mutation