Pilonidal disease is a chronic infection of the skin in the region of the buttock crease (Figure 1). The condition results from a reaction to hairs embedded in the skin, commonly occurring in the cleft between the buttocks.he disease is more common in men than women and frequently occurs between puberty and age 40. It is also common in obese people and those with thick, stiff body hair. Figure 1: Pilonidal disease is a chronic skin infection in the buttock crease area.