Pili annulati is a hair condition where alternating segments of light and dark hair are visible on individual strands when exposed to light. It can be caused by a genetic mutation and is often associated with hair loss. Treatment is not usually necessary, but further testing may be recommended if it is a symptom of another medical condition.
Pili annulati (PA), or ring hair, is a hair condition in which alternating segments of light and dark hair are visible on individual strands when exposed to bright or reflective light. The hair appears to be covered in shiny dots or streaks of color. The permanent, non-progressive condition can occur on its own, with alopecia areata, or be a symptom of a disorder called autosomal recessive hypohidrotic ectodermal dysplasia. Pili annulati usually develops by age two.
The exact cause of pili annulati is not known, but it is passed on through an autosomal dominant gene. Ringed hair can be caused by a metabolic protein deficiency leading to the abnormal formation of cytoplasmic ribosomes with the hair cells, resulting in the unusual formation of keratin within the hair cortex. Most cases are thought to be caused by a mutation in the keratin-forming cells of the hair follicle.
The diagnosis of pili annulati can occur after a visual examination of the hair strands by a doctor. A microscopic examination of the hair shaft may be needed to confirm the diagnosis. Under a reflected light microscope, irregular spaces are seen between areas of normal hair growth. The empty spaces within the strand reflect light, giving the impression of rings or dots within the strand. Hair strands usually lack the full amount of keratin normally found in most hair.
The symptoms of pili annulati are varied. In addition to the different colored bands on each strand of hair, the hair can be abnormally brittle. Hair loss often occurs due to rapid breakage of hair strands. An adult with PA may notice that armpit hair and other body hair have the same ring-like appearance.
Pili annulati does not usually require any treatment. Medicated shampoos that promote hair regrowth may be recommended to treat possible hair loss. Gentle brushing can help brittle strands of hair stay whole. Because ringed hair can be caused by or be part of another medical condition, a doctor may recommend further testing if your hair strands show signs of pili annulati.
Autosomal recessive hypohidrotic ectodermal dysplasia is characterized by malformations of the hair, teeth and skin. A person with this condition may also have missing teeth and very thin hair. Small, hard bumps called follicular hyperkeratosis often develop on the body, arms, and legs. A skin biopsy will show that the sweat glands have not developed.
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