The body hair of Asians differs from that of other races in a number of ways. Asians have shorter, straighter, thinner, and less body hair than Caucasians and black individuals. Since a case reported by Itin et al.1 in 1994, research studies of knotted body hair have rarely been reported.

A 26-year-old Korean man complained of the increasing density of knotted body hairs on his arms and legs (Fig. 1). He was in good health, and his medical histories were not specific. The patient had rubbed his body everyday using a towel with cleanser after he felt a crawling sensation on his body. He believed this weird sensation occurred after sexual contact with an unknown female 4 months prior. The results of the laboratory tests showed no abnormal findings in complete blood count, blood chemistry, immunoglobulin E level, venereal disease research laboratory test, and Treponema pallidum hemagglutination test. A physical examination showed no significant signs, such as indications of parasitic infestation. Interestingly, the patient had mild skin xerosis and approximately ten knotted hairs on both of his upper and lower extremities. We removed a sample of knotted hair for further examination. Light microscopy revealed that the knotted hairs originated from different hair follicles. To investigate the ultrastructural characteristics of the hairs, scanning electron microscopy (SEM, S-4700; Hitachi, Tokyo, Japan) was used. SEM showed knotting of several hair shafts from different hair follicles due to sudden curvature; there was no mechanical fracture or fissuring of the hair shafts. Although Barbareschi et al.2 previously reported the presence of yeast colonies on lesional hairs, we were unable to find any yeast colonies on the hair samples, and the roots of the hairs looked normal (Fig. 2).

Twisted and rolled body hairs are an uncommon hair disorder that result in knotted and twisted hair. Moreover, The pathogenesis of matting of hair is poorly understood. However, previously published research indicates that the condition could be caused by both acquired defects3 and autosomal traits1. The differential diagnosis of hair matting includes trichonodosis, circled hairs, and pili multigemini. In this particular case, the patient did not have any of the features associated with these conditions. Wilson et al.4 reported matting of scalp hair as a result of shampooing and harshly rubbing to make hair stick together. Shelly et al.5 have described vellus hair knots that resulted from rubbing a powder puff on the skin. The present patient had a similar causative factor, namely, mechanical forces from severe rubbing because of a sanitary concern. Although further studies are necessary to pinpoint the exact pathogenesis, this finding allowed us to confirm that this disorder likely originated from an acquired trait activated by a mechanical cause.

There are reports of knotted body hair, but they are only found in the Caucasians; because the body hair of Asians tends to be short, of low density, and straight, it is difficult to knot the hair. Thus, we considered the case quite rare, particularly considering that the individual is Korean.