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Uncombable hair syndrome, also known as Pili trianguli et canaliculi and Spun glass hair is a rare structural anomaly of the hair with a variable degree of effect. It was discovered in the 1970's[1] It becomes apparent from as little as 3 months to up to 12 years. The hair is normal in quantity and is usually silvery-blond or straw-colored. It is disorderly, it stands out from the scalp, and cannot be combed flat. The underlying structural anomaly is longitudinal grooving of the hair shaft, which appears triangular in cross section. There usually is no family history, though the characteristic hair shaft anomaly can be demonstrated in asymptomatic family members by scanning electron microscopy. To be noticeable, 50 % of hairs must be affected by the structural abnormality. Improvement often occurs in later childhood.[2][3] An autosomal dominant mode of inheritance has been suggested though a autosomal recessive pattern with varying degrees of penetrance has also been noted.[1][2] The stiffness of the uncombable hair has been reasoned to be due to the triangular form of the hair shaft in cross section. It has been suggested that the condition may result from premature keratinization of the inner root sheath.[2] Other syndromes with hair abnormalities may also show features of uncomable hair syndrome such as Rapp-Hodgkin ectodermal dysplasia, loose anagen hair syndrome, EEC syndrome (ectodermal dysplasia, ectrodatyly and cleft lip/palate) and familial tricho-odonto-onchyial ectodermal dysplasia with syndactyly. However unlike these conditions, uncombable hair syndrome alone is not associated with physical, neurologic, or mental abnormalities.[1]
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