Typical pilonidal sinus disease (PSD) occurs in the natal cleft i.e. sacrococcygeal region.
However, some occupation related pilonidal sinuses occur in webs of fingers e.g. hair dresser, sheep shearer, dog groomer, slaughterman or milker.
Other locations where pilonidal sinuses may occur include: penis shaft, axilla, intermammary area, groin, nose, neck, cltoris, suprapubic area, occiput, prepuce, chin, periungual region, breast, face and umbilicus.
Umbilical PSD typically occurs in young hairy males with a deep umbilicus. Explanations offered include: wearing tight clothes causing hair to be inserted as well as wearing a belt causing hair to accumulate. Poor hygiene is often quoted but this is an unproven oversimplification. Hair removal is all that may be required however a recent randomized study showed surgical excision was superior.
Umbilical pilonidal sinus from Eryilmaz R
Penile PSD typically occurs in uncircumcised men around the corona. Hair removal followed by circumcision may be required.
Intermammary PSD typically occurs in overweight women. The tract almost always runs in a caphalad direction to a secondary sinus which is away from the midline. Excision is often required.
Gupta PJ et al. 1999 Unusual sites and presentations of pilonidal sinus disease.
Eryilmaz R et al. 2005 Umbilical Pilonidal Sinus Disease: Predisposing Factors and Treatment.
Doll DHO et al. 2015 Stop insulting the patient: neither incidence nor recurrence in pilonidal sinus disease is linked to personal hygiene.