Etiology
Although historically thought to be a congenital disease, pilonidal disease is now accepted as an acquired disease in which loose hairs trapped within the natal cleft penetrate the skin leading to a granulomatous foreign body reaction.[4] As a result, midline pits within the natal cleft and chronic sinus tracts may develop. Although less common, pilonidal disease may occur in other locations such as the interdigital spaces and between breasts, supporting an acquired etiology. In all locations, the hairs penetrate the skin creating a sinus and/or cyst.[5][6][7]
Pathophysiology
The exact mechanism leading to the development of pilonidal disease is unknown.[4]
According to one hypothesis, the inciting factor is an empty hair follicle that becomes filled with keratin and debris which subsequently results in loose hair being trapped within the follicle. An inflammatory reaction follows resulting in a granuloma within the follicle and subsequent development of a sinus tract.[8] Due to the natural environment of the natal cleft, the tract becomes superinfected resulting in acute pilonidal disease. Following the initial presentation, the sinus tract continues to drain resulting in a chronic condition.[9]
Another theory attributes pilonidal disease to the loose hairs that collect within the natal cleft from various parts of the body. Due to natural depth of the natal cleft, the loose hairs easily penetrate the skin because of its low resistance, and generate an inflammatory reaction with subsequent development of cysts and/or sinus tracts.[10]
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