Pili annulati, or 'ringed hair,' is a disorder in which scalp hairs show alternating light and dark bands. It is often an incidental finding, and the hair usually does not show increased fragility (Green et al., 2004). ... Pili annulati, or 'ringed hair,' is a disorder in which scalp hairs show alternating light and dark bands. It is often an incidental finding, and the hair usually does not show increased fragility (Green et al., 2004). See also pseudopili annulati (613241), a distinct entity.
Cady and Trotter (1920) reported 3 unrelated families with ringed hair. The condition was restricted to hairs on the scalp. Based on refractive patterns under transmitted and reflective light, Cady and Trotter (1920) concluded that the light areas ... Cady and Trotter (1920) reported 3 unrelated families with ringed hair. The condition was restricted to hairs on the scalp. Based on refractive patterns under transmitted and reflective light, Cady and Trotter (1920) concluded that the light areas were caused by the presence of gas in the interstices of the medulla and cortex of the hair shaft, and not by lack of pigmentation. Ashley and Jacques (1950) reported a 4-generation pedigree with ringed hair inherited in an autosomal dominant pattern. Grossly, affected scalp hairs showed alternating light and dark bands with sharp demarcation. When observed en masse, hair appeared lusterless, graying, sandy-colored, or speckled. In some cases, affected hairs were shorter than unaffected hairs due to breakage at the light, gas-filled segment. Ashley and Jacques (1950) concluded that pili annulati was distinct from beaded hair, or monilethrix (158000). Pili annulati hairs are cylindrical throughout the shaft with no change in hair circumference, whereas those of monilethrix have constrictions in the hair at regular intervals. In addition, individuals with pili annulati usually have normal growth of hair, whereas those with monilethrix have alopecia as well as associated follicular keratosis.