P8   PILI ANNULATI: CHARACTERIZATION OF THE PHENOTYPE

^1,3Jack Green, ²David de Berker, ³Libby Fitzpatrick, ³Sue Forrest, ¹Rod Sinclair; ¹Department of Dermatology, St.Vincent’s Hospital, Melbourne, Australia; ²Bristol Royal Infirmary Bristol; England; ³ Murdoch Childrens Research Institute, Melbourne, Australia

Examination of 15 affected and 17 unaffected individuals from three families with pili annulati with 32 age and sex matched controls revealed that ¾ of pili annulati cases are subclinical. Clinical detection was largely proportional to the percentage of hairs detected on light microscopy.  The phenotype of this disorder is extremely variable. This ranges from a small number of hairs affected in only part of their length with lesions only extending across part of the width of the hair to gross examples, with a majority of hairs affected through out their length and bands extending the full width of the hair. Partial variations of pili annulati banding are present either centrally or eccentrically. There was no relationship with the presence or absence of a visible medulla. The features of pili annulati were clearly distinguishable from the medulla on morphological grounds. Pili annulati appeared as focal longitudinal areas composed of numerous dark strands, at times associated with an alteration of the overlying surface of the hair shaft. The medulla appeared as multiple vacuolations within the central region of the hair shaft, with or without pigment. This was present in discrete segments or continuously along the hair shaft. No features of pili annulati were detected in the controls.

Clear phenotype assignment is a prelude to genetic linkage studies for this disorder. Appropriate candidate areas include the hairless gene on chromosome 8, and the hard keratin clusters on chromosomes 12 and 17.