Until the middle of the 20th century, it was assumed that the pilonidal cyst was congenital and the development of the fistula already took place in the embryo.
- Congenital fistulas of the coccyx do indeed occur:
- In rare cases, a pilonidal cyst in the fetus can be visualized by ultrasound as part of a prenatal examination.
- Newborns born with spinal cord and spinal canal anomalies often show a pilonidal cyst.
- Some medications taken during pregnancy can cause a pilonidal cyst in the newborn. These include, for example, the high-dose intake of phenytoin, a drug for the treatment of epilepsy.
- Another argument in favour of a genetic predisposition would be that a family history of pilonidal cyst can be observed. In a family history, the first symptoms often appear very early and the fistulas of the tailbone tend to reappear after treatment.
- Another congenital problem is that the pilonidal cyst is always located in or immediately near the midline of the buttocks region, where problems in the development of the fetus often occur during the embryonic period.
However, there is also some evidence against the assumption that the pilonidal cyst is exclusively congenital:
- An inflamed pilonidal cyst is rarely observed before puberty, and if it does, it occurs 4.5 times more frequently in boys than in girls.
- Another argument against this is that in the case of malformations of the spinal cord and spinal canal, the hair nest of the pilonidal cyst does not contain any scattered skin appendages such as sweat or sebaceous glands, as one might expect with a congenital problem.
- Nor does the theory of congenital tailbone fistula explain why in the majority of cases the disease only becomes apparent during puberty and then predominantly occurs in men with a stronger fat cushion over the coccyx
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Acquired disease with a questionable genetic predisposition
Pilonidal cysts and tailbone fistulas are nowadays regarded as a disease acquired during puberty in which there may be a genetic predisposition. The fistula formation is triggered by the rubbing movements of the buttocks, which causes broken hair to twist into the skin. This creates depressions in the skin that can contain hair, the so-called pits.
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The horny scales of the hair act like barbs, whereby the hair can penetrate deeper and deeper into the subcutaneous fatty tissue. This is where a foreign body granuloma develops.
Foreign body granulomas do not heal spontaneously. They do not necessarily cause symptoms (asymptomatic form) but can become infected. The consequences are discomfort when sitting, a feeling of pressure or even small, bloody secretions (chronic form) as well as the abrupt development of abscesses (acute form).
The development of the tailbone fistula is favoured by additional factors. These include strong hairiness, overweight, excessive sweating, a strong fat cushion over the tailbone as well as a deeply absorbed bottom fold. A predominantly sedentary activity also has a favourable effect. This has led to the designation "jeep´s disease" among soldiers since during the Second World War between 1942 and 1945 more than 77,000 American soldiers fell ill with a tailbone fistula.
It is often claimed that a lack of personal hygiene is an additional risk factor. However, studies have shown that hygiene behaviour has no influence on the formation, abscess formation or recurrence of the tailbone fistula.
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