A novel monilethrix mutation in coil 2A of KRT86 causing autosomal dominant monilethrix with incomplete penetrance

Monilethrix is a genetic hair shaft disorder that causes a dystrophic alopecia. Mutations causing autosomal dominant monilethrix have been found in the helix initiation and helix termination motifs of the type II hair keratins KRT81, KRT83 and KRT86. Mutations in DSG4 are linked to recessive transmission.

We investigated a large Tasmanian family demonstrating autosomal dominant monilethrix with incomplete penetrance in order to identify the responsible genetic mutation. As only some affected hairs were moniliform, analysis was undertaken to demonstrate a deficit in the tensile strength of nonmoniliform hairs.

One hundred and twenty family members were examined. Light microscopy of hair samples was used to support clinical diagnoses. Linkage and gene sequencing studies were then undertaken. Nonbeaded fibres were analysed using the Single Fibre Analyser 3 (SIFAN 3).

We identified a novel A280V (c.839C > T substitution) mutation in the coil 2A region of KRT86. This is the first mutation located in a region other than the helix initiation or termination motifs. The A280V mutation was identified in both affected and clinically unaffected family members. Nonmoniliform hairs demonstrated reduced elasticity among both affected and unaffected individuals carrying the A280V mutation.

This is the first mutation located in a region other than the helix initiation or termination motifs, thus expanding the spectrum of mutations and highlighting the importance of molecular diagnosis in monilethrix.