The Journal of dermatology
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The etiology of pilonidal sinus remains controversial. Some think it is congenital, and others think it is acquired. ⋯ 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.