By Gary M. White, MD

Pili annulati (PA) is a rare hair shaft abnormality characterized by alternating light and dark sections of hair visible to the naked eye occurring randomly. The condition is a little harder to appreciate in dark hair. The hair shaft may be of normal strength or it may be fragile. Examination under the microscope shows the light hairs to be normal and the dark areas to be filled with air. In contrast, if the hair is viewed with reflected light, the gas-filled areas are light and the normal hair is dark.


As the hair lightens with age, the condition can become more noticeable. Dying the hair may be tried. The appearance is actually considered pleasing by many.

Differential Diagnosis

See fragile hair.


A 49-year-old African-American woman was being evaluated for central centrifugal cicatricial alopecia, and was found to have alternating light and dark bands of the hair shafts. Trichorrhexis nodosa was also found. Dermatology Online Journal 18(8)


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