Circle hair: report of two cases and brief review of the literature.

Circle hair (CH) is an interesting subtype of ingrown hair, characterized by the growing of hair shaft in a spiral or circular morphology underneath a translucent layer of stratum corneum, parallel to skin surface. In contrast to rolled hair (RH), neither perifollicular inflammation nor abnormal follicular keratinization are known to accompany CH. The reason why the hair shaft grows circumferentially and transversely under the skin instead of emerging through an apparently open hair follicle ostium and growing vertically remains to be determined. Although CH is a frequent benign incidental finding in normal skin examination, reports on this disorder are scarce. Herein we report two cases of CH and briefly review the existing literature. We believe that CH develops because of trauma in patients having a genetic susceptibility for this disorder and that CH is more common than the relevant medical literature suggests.