The origin of pilonidal sinus: a case report.

The etiology of pilonidal sinus remains controversial. Some think it is congenital, and others think it is acquired. It is difficult to distinguish acquired pilonidal sinus from congenital, because infection almost always complicates both. We report here one case of acquired pilonidal sinus unaccompanied by infection. Histological examination showed that no epidermis or hair follicle was present in the inner wall of the sinus. This case shows that acquired pilonidal sinus is due to invasion of external hairs and that this condition needs to be distinguished from congenital pilonidal sinus.