Pilonidal sinus (PNS) is a developmental benign lesion, which is commonly presented in hair-bearing areas exposed to continuous pressure friction. Thus, it is frequently seen at the sacrococcygeal region in between the buttocks. From the pathogenesis point of view, this lesion occurred through the interaction of three main predisposing factors: first is the presence of optimum levels of the sex hormones required for sufficient maturation of body sex criteria, which leads to the second factor that enhancement of the hair growth as a part of the normal sex development. The third factor is a mechanical factor in form of the presence of frequent pressure friction at the zones of active hair growth. Therefore, the incidence of this lesion becomes higher at the puberty age group, among which there will be the highest activity of hair growth. In the presence of persistent pressure friction, the actively growing hair will be pushed and affected inward resulting in the formation of a hole or tunnel at the skin. This tunnel may be got filled with fluid or pus accumulation because of the lack of proper personal hygiene at these areas and superadded infection leading to abscess collection. The lumen of the sinus itself will provide a significant negative pressure that cause more hair nesting and furthermore tunnel dilation, which causes more drawing in more hair, therefore the cycle will be perpetuated [1,2,3].
Historically speaking, The term pilonidal was first given by R. M. Hodges in 1880, and it is a Latin term, pilo for hair and nidal for nest, thus pilonidal a phrase that described the gross pathological morphology of this lesion as a nest of hair. For the first time, this lesion was discovered during Second World War among young soldiers who were exposed to the long-standing pressure frictions on their bottoms during prolonged war Jeep cars deriving, therefore at that time, this lesion was named as Jeep rider’s disease or Jeep bottom disease [4, 5].
In addition, from the epidemiological point of view, the incidence rate of this condition is 26:100,000. The males are more affected than the females; the male-to-female ratio is 3-4:1. In accordance, the young men were showed the highest incidence for this lesion, and the age of highest incidence was 20 years [5,6,7,8].
The PNS constitutes an important clinical entity; it may be associated with recurrent attacks of infection, because it usually occurs at the dirtiest high-humidity zones of the body, and with a lack of proper local personal hygiene and care, this will lead to the persistence of purulent discharging sinus. In addition, as a rare situation of PNS, the constant chronicity of the infection may lead to the change of the benign keratinizing squamous cells to malignant cells resulting in the development of squamous cell carcinoma [8,9,10,11,12].
The management of PNS is surgical. Patients with mild to moderate disease can be treated by simple techniques like the Bascom-1 procedure, which can be done under sedation and local anesthesia. Other procedures include Munro Z-plasty, Karydakis procedure and its Kitchen and Bascom-2 modifications, and En bloc excision of the cyst. In addition, the Limberg flap technique was very useful too [13,14,15,16,17].
Although the sacrococcygeal region was the commonest site for the development of this lesion, but also this lesion was diagnosed at the scalp, neck, axilla, around the umbilicus, pubic region, groin, penis, and interdigital web region. However, the external ear is deemed the rarest site for the occurrence of this lesion, up to our knowledge, there were two cases of pilonidal sinus of the external ear recorded in the world, one at the ear lobule and the other one at the EAC. Thus, our case can be considered as the second case of pilonidal sinus that was diagnosed in the world [1, 6].
Indeed, this case presentation becomes unique because it is not in line with the usual and well-established presentation of this lesion. Thus, we tried via this case report to illustrate invaluable aspects of this case, which makes the lesion unforeseen.