B4.4 A GENETIC LOCUS FOR PILI ANNULATI

J. Green¹², E Fitzpatrick², D de Berker³, S Forrest², R Sinclair¹

¹Department of Dermatology, St. Vincent’s Hospital, Melbourne, Australia: ²Murdoch Childrens Research Institute, Melbourne, Australia ³Bristol Dermatology Centre, Bristol Royal Infirmary, Bristol, England, UK

Objectives: Pili annulati is a non-fragile hair shaft disorder characterised by banding. A genetic locus for this disorder has not previously been identified. We sought to identify a genetic locus associated with this disorder in two families by clinical and microscopic examination of hairs and linkage analysis.

Methods: Two families’ pedigrees (G and B) were studied. All subjects were clinically examined and then hair samples were microscopically examined. Genomic DNA was extracted from blood. A 5 cM genome widescan was performed on pedigree G using dinucleotide microsatellite markers. Linkage analysis was performed using the MLINK program.

Results: In both pedigrees pili annulati segregated in an autosomal dominant manner. An 11.07 cM locus was identified on chromosome 12 with a maximum LOD score of 3.59 in pedigree G. Linkage analysis at the same marker in pedigree B revealed a LOD score of 0.89 to give a combined LOD score (assuming no locus heterogeneity) of 4.49.

Conclusions: We have, for the first time, identified a candidate genetic locus for pili annulati. This should, in time, lead to the identification of a causative genetic mutation and improve our understanding of growth control of the hair shaft.