Cheveux incoiffables--diagnostic, clinical and hair microscopic findings, and pathogenic studies.

Three possible mechanisms of the hair shaft abnormality in cheveux incoiffables have been investigated in nine patients. Cheveux incoiffables hairs were found to exhibit a normal distribution of cystine-rich protein within both the cuticle and the cortex, as determined by silver methenamine ultrastructural cytochemistry. Resistance to stretching, at 65% relative humidity and constant temperature, was similar to normal controls. Resistance to bending forces was also assessed, and was equivalent in both groups. On scanning electron microscopy, all patients with cheveux incoiffables demonstrated longitudinal grooving of the hair shaft, and the hairs were triangular or heart-shaped in cross-section. In addition, there appeared to be minimal cuticular weathering. Even hairs of 20-30 cm length showed only minimal cuticular and cortical weathering, compared with normal hair shafts of similar length and diameter. It is possible that the reduced progressive weathering renders the hair shaft more rigid, and could serve to explain the 'stand on end' appearance of the hair which is typical of this condition. However, the characteristic cross-sectional shape of the hair shaft in cheveux incoiffables may render it more rigid and resistant to bending forces. This latter theory has yet to be fully investigated.