Abstract: 【Abstract】 Objective To detect mutations of the type Ⅱ human basic hair keratin （hHb） gene in a family of Han nationality with monilethrix. Methods Clinical data were collected from a family of Han nationality with monilethrix. Dermoscopy was performed to observe hairs of the family members, and light microscopy and scanning electron microscopy （SEM） were conducted to investigate the features of lesional hairs. Blood samples were obtained from the proband, other family members and 100 healthy controls, and DNA was extracted from these blood samples. Polymerase chain reaction （PCR） was performed to amplify the exons 1 and 7 of the hHb1, hHb3 and hHb6 genes, and DNA sequencing results were compared with their sequences in the GenBank database. Results The proband was an 8-year-old girl, whose head hairs had become fragile and easy to pull out since 2 months after birth. Skin examination showed diffuse sparse hairs, most of which were 2-cm-long broken hairs with abnormal appearance. Moniliform hairs were scattered all over the head, especially on the occipital region, and follicular keratotic papules were observed on the back of the neck. The proband was diagnosed with monilethrix. There were a total of 15 members in the 3-generation family, and 4 were diagnosed with monilethrix. The hair shafts of the 4 patients all showed typical moniliform structures. After 9-month consecutive treatment with topical minoxidil 2% solution, the hairs of the proband turned longer and denser. A heterozygous mutation c.1237G>A （p.E413K） was identified in the exon 7 of the hHb6 gene in the 4 patients, but not in the other family members or 100 healthy controls. Conclusion The E413K mutation of the hHb6 gene was firstly found in the patients in a Chinese Han family with monilethrix, which may be responsible for moniliform hairs.

Key words: Monilethrix, Pedigree, DNA mutational analysis, Minoxidil, Genes, hHb6