Quantitative assessment of scanning electron microscope defects in uncombable-hair syndrome.

Uncombable-hair syndrome is a rare disorder of scalp hair that starts early in childhood. It is characterized clinically as unruly hair and by scanning electron microscopy as longitudinally grooved hairs with a triangular cross section. Because of the controversy of inheritance and prior reports of similar changes in normal and other hair disorders, we performed a quantitative scanning electron microscopic assessment of four patients with uncombable-hair syndrome, first-degree relatives, and nonaffected controls. Our results indicate that longitudinal grooving of scalp hair is a common occurrence, and that for clinical changes to be apparent, approximately 50% of hairs must be affected.