Pilonidal disease was first described by Mayo1 in 1833 who hypothesized that the underlying etiology is incomplete separation of the mesoderm and ectoderm layers during embryogenesis. In 1880, Hodges2 coined the term pilonidal sinus; he postulated that sinus formation was incited by hair.2 Today, Hodges theory is known as the acquired theory: hair induces a foreign body response in surrounding tissue, leading to sinus formation. Although pilonidal cysts can occur anywhere on the body, they most commonly extend cephalad in the sacrococcygeal and upper gluteal cleft (Figure 1).3,4 An acute pilonidal cyst typically presents with pain, tenderness, and swelling, similar to the presentation of a superficial abscess in other locations; however, a clue to the diagnosis is the presence of cutaneous pits along the midline of the gluteal cleft.5 Chronic pilonidal disease varies based on the extent of inflammation and scarring; the underlying cavity communicates with the overlying skin through sinuses and often drains with pressure.6
Figure 1. Pilonidal sinuses showing with multiple open and scarred sinus tracts on the bilateral buttocks and gluteal cleft of a hirsute man.
Pilonidal sinuses are rare before puberty or after 40 years of age7 and occur primarily in hirsute men. The ratio of men to women affected is between 3:1 and 4:1.8 Although pilonidal sinuses account for only 15% of anal suppurations, complications arising from pilonidal sinuses are a considerable cause of morbidity, resulting in loss of productivity in otherwise healthy individuals.9 Complications include chronic nonhealing wounds,10 as recurrent pilonidal sinuses tend to become colonized with gram-positive and facultative anaerobic bacteria, whereas primary pilonidal cysts more commonly become infected with anaerobic and gram-negative bacteria.11 Long-standing disease increases the risk of squamous cell carcinoma arising within sinus tracts.10,12
Histopathologically, pilonidal cysts are not true cysts because they lack an epithelial lining. Examination of the cavity commonly reveals hair, debris, and granulation tissue with surrounding foreign-body giant cells (Figure 2).5
Figure 2. A shave biopsy specimen of a pilonidal sinus demonstrated dense inflammation and erosion bordering a sinus tract lined by granulation tissue and stratified squamous epithelium (A)(H&E, original magnification ×4). The sinus tract connects with a chronic abscess cavity that contains foreign-body giant cells, plasma cells, and neutrophils (B)(H&E, original magnification ×40).
The preferred treatment of pilonidal cysts continues to be debated. In this article, we review evidence supporting current modalities including conservative and surgical techniques as well as novel laser therapy for the treatment of pilonidal disease.