Congenital Defects of the Hair Shaft

Genetic defects influencing hair growth and quality are associated with a number of conditions characterized by hair breakage, misshapen hair shaft, sparse hair and abnormally colored hair. Congenital abnormalities of the hair shaft are relatively uncommon. Suspected congenital abnormalities should be examined by a physician.

Hair shaft abnormalities due to genetic defects of hair production include:

• Trichothiodystrophy-brittle hair, intellectual impairment and short stature; hair shafts have an abnormally low sulfur content.



• Pili annulati (ringed hair)-hair shafts have alternating light and dark bands.



• Wooly hair-hair is tightly coiled over the entire scalp.



• Uncombable hair-also called spun glass hair; the hair shafts have a triangular cross-section.



• Trichorrhexis invaginata (bamboo hair)-bamboo-like nodules on the hair shaft are caused by dysfunctional keratinization of the shaft.