Pathogenesis in pili torti: morphological study.

To clarify the mechanism of pili torti formation, hair materials obtained from a patient with the typical classical type of pili torti were examined. Light microscopy, scanning electron microscopy (SEM), transmission electron microscopy, (TEM) and 3-D analysis revealed that: (1) The hair shaft was partly flattened. The hairs twisted clockwise or counter-clockwise on their own axis and some hairs were knotted. (2) Short hairs showed disruptions at the flattened or unflattened regions, at the knot, or at the root of branched hairs caused by longitudinal ruptures. (3) Light microscopically, cell vacuolation and irregularity in thickness of the outer root sheath (ORS) at the suprabulbar level were seen. At the middle to upper levels of the follicles, some eosinophilic pyknotic ORS cells were observed scattered around. (4) At the upper levels, the ORS and inner root sheath (IRS) partly revealed irregularity of thickness and formed an irregular-shaped hair canal. (5) By DACM staining, cytoplasmic SH fluorescence showed an irregular arrangement of the ORS cells. Some abnormal SH- or SS-positive cells were observed scattered throughout the ORS. (6) Ultrastructurally, the irregularities in thickness and cell shape of the IRS and ORS became visible at the level, where the Henle's layer keratinized. In the hair cortex, there was no abnormality of nuclei and the keratin fibers were normally produced, although fibers were partially wavy. (7) By 3-D analysis, hair twist was already seen at the middle level of the hair follicles.(ABSTRACT TRUNCATED AT 250 WORDS)