Uncombable hair syndrome

Uncombable hair syndrome (UHS), also known as spun glass hair syndrome, pili trianguli et canaliculi, or cheveux incoiffables, is a rare disorder of the hair shaft characterized by dry, frizzy, spangled hair that is resistant to being combed flat. The condition typically becomes apparent between 3 months and 12 years of age, most commonly during infancy or early childhood. The hair is usually silvery-blond or straw-colored and grows in multiple directions, standing away from the scalp. Under scanning electron microscopy, the hair shafts display a characteristic triangular or kidney-shaped cross-section with longitudinal grooves or canals running along the surface, which distinguishes UHS from other hair shaft disorders. The condition primarily affects the scalp hair, while eyebrows, eyelashes, and body hair are typically normal. UHS is generally an isolated finding without associated systemic abnormalities, though in rare cases it has been reported in association with other ectodermal abnormalities or syndromes. The hair abnormality is caused by mutations in genes involved in hair shaft formation, most commonly PADI3 (peptidylarginine deiminase 3), TGM3 (transglutaminase 3), and TCHH (trichohyalin), all of which play roles in the structural integrity of the inner root sheath and hair shaft. There is no specific treatment for uncombable hair syndrome. The condition is generally benign and tends to improve spontaneously with age, often showing significant improvement by late childhood or adolescence as the hair becomes more manageable. Gentle hair care practices, including the use of soft brushes and mild conditioners, are recommended to minimize hair breakage. Biotin supplementation has been reported anecdotally to improve hair quality in some cases, though robust clinical evidence is lacking. The prognosis is excellent, as the condition does not affect overall health.

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