A Unique Presentation of a Pedal Pilonidal Cyst

A pilonidal cyst is a chronic condition typically involving a sinus or fissure caused by a hair follicle penetrating the skin. These cysts most commonly develop in weight-bearing, hair-bearing areas of the body, particularly in the sacrococcygeal region.^1-4 A subset of pilonidal cysts, known as “barber cysts” or “occupational pilonidal cysts,” occurs in individuals with prolonged exposure to excessive human or animal hair.^1-3 In such cases, hair penetrates the skin, leading to cyst formation in atypical, non-weight-bearing, or less hair-bearing areas. Reports have highlighted cases of pilonidal disease in unusual locations, such as the sole of the foot or dorsum of the hand, underscoring the diversity in presentation.^1,2,4,5

Case Presentation

A 56-year-old male with a past medical history of hypertension and obesity presented to the office with pain between the second and third toes of his left foot, localized in the second interdigital space. He works as a cook and has not had any previous pedal or orthopedic surgeries. The patient reported noticing a small “bump” about 1 week prior that progressively enlarged and became intensely painful. Earlier in the week, his daughter, a registered nurse, attempted to drain the lesion with a needle, resulting in the release of pus and a hair. Despite this intervention, the pain persisted, worsening with touch, shoe wear, and ambulation.

The physical exam showed present pedal hair, warm, moist skin, palpable pulses, and the described painful lesion. Neurovascular status was intact. Between the second and third digits there was mild edema, no erythema, and a small, exquisitely tender, 2mm raised nodule with a small pinpoint opening distally and 5mm proximally. There was no drainage and no signs of acute infection beyond extreme tenderness to palpation. There was no fluctuance or evidence of a mass beneath the skin. At this time, the clinical suspicion became higher for a pilonidal cyst due to the 2 small holes that tunneled and communicated with each other beneath the small nodule.

Pilonidal disease in the interdigital space is uncommon but has been described in cases linked to occupational exposure to hair or foreign debris.^2,4-6 Thus, clinical suspicion for this condition emerged during the work-up. Radiographs revealed no osseous or soft tissue abnormalities. We discussed treatment options with the patient, including conservative management with shoe modifications, such as wearing wide toe box footwear to prevent irritation and compression of the toes. We also presented an approach involving cyst aspiration, fluid drainage, and steroid injection adjacent to the aspiration site. After a full informed consent discussion, including risks, benefits, and potential complications, the patient opted for an interventional approach.    

We decided to perform the procedure in the podiatry clinic under local anesthetic after discussion with the patient. He received a local “V” block of the surrounding area with 10 mL of a 1:1 mixture of 2% plain lidocaine and 0.5% plain bupivacaine. The surgeon made a 0.5 cm incision in the second interdigital space using a #15 blade to connect 2 small, circular tunnels extending to the subcutaneous fatty layer of the skin. The cyst itself was not intact or visualized as fully intact. A pickup instrument helped the surgeon to extract a small cluster of hair within the ruptured cyst, and the area was milked to evacuate less than 1 mL of purulent drainage. The extracted sample was placed in a specimen cup for pathology, although it was not successfully delivered to the lab. Irrigation of the incision consisted of 50 cc of normal saline. No further tunneling or undermining was evident. Incision closure took place using 2 simple interrupted 3-0 nylon sutures (Figures 1,2). The postop dressing consisted of nonadherent gauze, 4x4s, and fluffed gauze overlay. There was very minimal drainage, negating the need for drain placement. The surgeon scheduled the patient for a follow-up 1 week later.

Histopathological evaluation is often recommended for pilonidal cysts, especially those occurring in atypical locations, to confirm the diagnosis and rule out other potential conditions such as epidermoid cysts or malignancy.^1,5-9 While a sample containing hair and purulent material was sent to pathology for evaluation, it was unfortunately lost in transit to the laboratory. This did not change the postoperative care, as the patient returned to clinic 1 week later and reported symptom improvement. If there was recurrence, (return of a painful nodule or signs of infection) we then planned to perform the same procedure and send the recurrent cyst to pathology.

The association between pilonidal disease and foreign body penetration, such as hair splinters, is well-documented in both occupational and nonoccupational contexts.^4,7-9 This unique etiology often necessitates surgical intervention when conservative measures fail. Additionally, pathology testing may confirm the diagnosis.

The patient tolerated the procedure well but expressed significant concerns about pain management, later achieved with one week of opioid medication postop. He received instructions to weight-bear as tolerated in supportive shoes, apply ice behind his knee, and elevate to help decrease swelling and help with pain. Suture removal was 2 weeks post procedure without incident. Postop the patient did well and healed without incident, stating that his pain and symptoms resolved within a few days. (Figure 3). The patient is now 6 months post-procedure, has healed without incident, and with no recurrence.

Conclusion

This case highlights the uncommon presentation of an interdigital pilonidal cyst in a patient without occupational exposure to hair, underscoring the variability of pilonidal disease beyond the typical sacrococcygeal region. Although rare, clinicians should consider these lesions in the differential diagnosis of painful interdigital masses, particularly in individuals whose professions involve exposure to hair or other fine debris. Proper clinical and surgical management, as demonstrated in this case, can alleviate symptoms and prevent recurrence. However, histopathological confirmation remains a critical component of the diagnostic process, especially in atypical cases. Further awareness and documentation of similar cases may enhance understanding and improve management strategies for this unique condition.

Dr. Santiago is a Podiatric Medicine and Surgery Resident at Ascension St. Vincent in Indianapolis.

Dr. Graves practices with Ascension Medical Group in Kokomo, Indiana. He is the current President of the Indiana Podiatric Medical Association and an Associate Attending with the Ascension St. Vincent Hopsital Podiatry Program in Indianapolis.
 

References
1.    Efthimiadis C, Ioannidis A, Koullias E, et al. Barber’s hair sinus in a female hairdresser: uncommon manifestation of an occupational disease: a case report. Cases J. 2008;1:1-4.  
2.     Kern AB. Pilar abscess of the toe: Occupational disease of hairdressers. Arch Dermatol. 1964;90(2):191-192.  
3.     Trüeb RM, Luu NC, Gavazzoni Dias MF. Not so uncommon cause of foot pain: Cutaneous hair splinter of the sole. Skin Appendage Disord. 2022;8(3):256-260.
4.    Morrell JF. Pilonidal sinus of the sole. AMA Arch Dermatol. 1957;75(2):269-269.  
5.     O’Neill AC, Purcell EM, Regan PJ. Interdigital pilonidal sinus of the foot. The Foot. 2009;19(4):227-228.  
6.     Rubio C, Pérez-Calderón R, Pérez-Ferriols A, et al. Interdigital pilonidal sinus in the foot. Clin Exp Dermatol. 2008;33(5):656-657.
7.     Salazar CA, Gonzalez JM. Hidden agony: foot pain linked to pet hair splinter. Cureus. 2024;16(6):e63530.  
8.     Salih A, Salih M, Ibrahim M. Pilonidal sinus of atypical areas: presentation and management. PSJ. 2017;3(1):8-14.  
9.     Shiratori T, Kawano N. Pilonidal disease on the dorsum of the hand and sole of the foot diagnosed by superficial echography. Indian J Dermatol. 2022;67(2):182-184.