F28 PILI ANNULATI: NEW HAIR SHAFT AND FOLLICLE FINDINGS WITH PEDIGREE ANALYSIS IN 3 FAMILIES

^1,3,5Feldmann KA, ²de Berker DAR, ¹Wolff H, ³Ferguson DJP, ⁵Pittelkow MR, ⁴Dawber RPR; ¹Dept. of Dermatolgy, Ludwig-Maximilians-University, Munich, Germany, ²Bristol Dermatology Centre, Bristol Royal Infirmary, Bristol, UK, ³John Radcliffe and ⁴Churchill Hospitals, Headington, Oxford, UK, ⁵Department of Dermatology, Mayo Clinic, Rochester, MN, USA.

Pili annulati is a condition of the hair shaft in which clinical examination reveals alternating light and dark bands. Transmitted light microscopy reveals the underlying abnormality as foci within the hair shafts which do not transmit light due to air-filled spaces in the hair cortex. Ten cases of pili annulati from three families were included in this clinical and morphological study. Analysis by light microscopy, scanning and transmission electron microscopy (n=10), morphological breakage analysis (n=10), amino acid analysis (n=1) and immunostaining of hair follicles (n=2) for keratins and basement membrane components was performed. Light microscopy confirmed the variable magnitude of the pili annulati focal abnormality (PAFA) within the hair shaft, ranging from a central trace to full thickness with associated cuticle disruption. Scanning electron microscopy revealed longitudinal folding and loss of cuticle at a periodicity compatible with PAFA. Distinct weathering changes present in some hair shaft may mask the primary fault. Transmission electron microscopy revealed abnormal spaces within the cortex consistent with an anatomical basis for PAFA. Amino acid analysis showed a significantly higher content of lysine in pili annulati hair shafts (3,34 mol%) compared to normal hair shafts (2,73 mol%). Immunostaining for different components within the basement membrane revealed a wavy lamina densa with partial duplication. This study highlights the spectrum of the phenotype in pili annulati, including a newly described weathering pattern associated with PAFA and demonstrates new immunohistochemical abnormalities within the follicle of pili annulati hair.