Ringed hair disease is a very rare disorder of the hair shaft. Clinical examination reveals alternating light and dark bands giving a shiny appearance to the hair. In most instances, the scalp is reported as the affected site, axillary and beard involvement has been described only rarely. Clinical expression is variable along the hair shaft and between different hairs of one individual. Scanning electron microscopy reveals that the light bands - (appearing dark under the light microscope) are due to air-filled cavities within the cortex of the affected hair shafts. The pathogenesis remains unknown. Transmission of this disorder is considered to be autosomal dominant, but sporadic cases have also been described. Recently, a gene locus responsible for the familial form has been mapped to chromosome 12q24.32-24.33. Differential diagnosis includes pseudopili annulati, an unusual variant of normal hair, which is due to periodic twisting and an elliptic shape in cross section of the hair shaft, reflecting light in such a way as to show similar banding. Ringed hair disease cannot be treated but the prognosis is favourable, hair growth is usually normal.
Last update: February 2005