Hair Loss: Hair Shaft Defects
One of the most common hair shaft defects a dermatologist encounters is trichorrhexis nodosa (also called trichonodosis). Trichorrhexis nodosa is a defect in the hair fiber. When observed under the microscope most of a hair shaft looks entirely normal. However, in isolated spots along the length of a fiber swelling and/or fraying can be seen. These focal defects develop where there is an absence of cuticle.
Causes of trichorrhexis nodosa can be congenital or acquired. The congenital form is very rare, but some people have naturally weak hair where the cuticle is not properly produced. Congenital trichorrhexis nodosa is usually hereditary, it runs in families, and first develops at a very young age. Abnormal production of irregular and brittle hair fibers can also occur in metabolic disorders such as those that involve abnormal urea synthesis, abnormal copper or zinc metabolism, or defective cysteine or sulfur incorporation into hair fiber (trichothiodystrophy).
Acquired trichorrhexis nodosa is much more common and develops as a result of excessive hair manipulation and overprocessing. Too much brushing, hairstyles that put constant stress on the hair, and excessive washing, dying, and perming may disrupt the cuticle in focal areas along a hair shaft. Trichorrhexis nodosa is particularly seen in people who overuse hot combs or permanent waves to style their hair. Once the cuticle is removed from hair fiber then the hair cortex swiftly breaks down.
Treatment depends on the cause of the focal defects. If the hair production is believed to be abnormal then treatment will focus on the hair follicle and improving the strength of hair fiber. Where the defect is the result of excessive grooming the obvious action is to reduce the amount of hair manipulation. People are encouraged to stop using brushes, avoid hair styling that involves chemicals, and use only very mild shampoos.
Published on March 1, 2010