Trichonodosis (knotted hairs) may affect any of the various types of hairs located on the body. Two types of trichonodosis are generally described: (1) a rare variety of undetermined etiology associated with abnormal hair growth and (2) a commoner variety resulting from physical and mechanical forces. The etiology, I believe, is purely mechanical whether the knotted hairs occur in normal or abnormal hair growth. The pubic and thigh regions are most frequently involved since curliness of the hairs in those areas predisposes them to knotting. Mechanical factors such as scratching, combing, washing or friction may produce tangling and knotting of hairs. Repeated encounter with these factors results in tightening of the knots. If the knots are pulled excessively tight, transverse splintering of the hair shaft and simulation of trichorrhexis nodosa may result. Cases resembling alopecia, due to the breaking off of the hairs at the knots, have been reported.
SCOTT MJ. TRICHONODOSISReport of a Case. AMA Arch Derm Syphilol. 1951;63(6):769–771. doi:10.1001/archderm.1951.01570060097011