Pseudopili Annulati

Description

Pseudopili annulati is an unusual variant of normal hair characterized by a banded appearance of the hair under reflective light, as observed in pili annulati (180600), but resulting from a distinct underlying physical defect. There is no increased hair fragility (Price et al., 1970).

Clinical Features

Price et al. (1970) reported a 9-year-old girl with blond hair whose scalp hair showed light and dark banding since infancy. Light microscopy showed that the banding appeared only if the light struck the hair at right angles to the long axis of the hair, which was distinct from that observed with pili annulati. Polarizing light indicated variability in the thickness of the hair shaft, and illuminating light did not show bands, 2 additional features that distinguished it from pili annulati. Further examination of the hair shaft showed that the pseudopili annulati hairs had periodic widening and narrowing, that the fiber cross-section was roughly elliptical, and that a periodic twisting of the hair (30 to 40 degrees in 2 alternating directions) was superimposed on the ellipticity. Price et al. (1970) concluded that the apparent banding of pseudopili annulati was due to superficial optical effects of the geometry of the twisted hair. There was no family history of a similar trait. Pseudopili annulati was considered a variant of normal hair, particularly apparent in individuals with blond hair.

Lee et al. (2001) reported pseudopili annulati in a 3-year-old Chinese girl with dark hair. Scalp hairs showed alternating shiny and dull segments, about 0.5 to 1.5-mm long, most clearly seen when light hit the hair at right angles to the long axis. Light and electron microscopic studies showed that the hairs were elliptical, appeared uniformly dark under transmitted light, and showed alternating thickness in diameter along the length. The hair also twisted along the long axis. No abnormal spaces were seen in the cuticle or cortex. Lee et al. (2001) noted that the flattened surfaces of the hair fiber act as reflective mirrors, thus resulting in a ringed hair appearance, even though there is no true banding, as in pili annulati. There was no family history of a similar trait.