Pilonidal disease is a common medical condition that accounts for almost 15% of anal suppurations [1]. It is a chronic inflammatory disease associated with the penetration of hair fragments into the skin. It occurs commonly in the sacrococcygeal region [2]. However, it may also occur in other areas rarely like umbilicus, nose, suprapubic area, axilla, groin, interdigital web, clitoris, prepuce, or penis [3]. The onset of pilonidal sinus is rare before puberty and after the age of forty [4]. It occurs three times more in male than female [4]. It clinically presents as mass, pain, cellulitis and redness [5].

Scalp pilonidal sinus is an extremely rare condition with only seven reported cases in literatures. Although trauma accounts for etiology of some cases, its exact cause remains unknown [2] [6] [7]. We present a case of scalp pilonidal sinus with literature review.

A 19-year-old male presented with a chronic nodule in the scalp for one year duration with intermittent discharge. There was no history of trauma. Local examination showed a single mobile nodule, 2x2 cm in size in the left parieto-occipital region with a punctum in center. Complete blood count, erythrocyte sedimentation rate and skull X-ray were normal. Complete excision of the nodule was performed under local anesthesia. Primary closure was done after irrigating the wound with diluted povidone. Histopathological examinations showed skin and subcutaneous tissue of scalp containing a sinus tract in the center infiltrated by mixed inflammatory cells, associated with foreign body giant cell reaction which contained hair particles. The wound showed clear margins after three months of the operation (Figure 1).

Pilonidal sinus refers to any subcutaneous sinus which contains hair [2]. It is a blind-end tract lined with granulation tissue, which leads to a cystic cavity lined with epithelial tissue [3]. The origin of pilonidal disease is not well understood. There are two theories associated with its pathogenesis: the acquired and the congenital theories. However, the majority of opinion favors the acquired theory [8] [9]. In general, at least three conditions need to be fulfilled for a pilonidal sinus to develop: First is hair in the skin and, second, some kind of wrinkled skin, such as the natal cleft or a scar. The third condition is a mixture of hormonal and hygienic problem [7]. It usually presents as pain, local inflammation and redness [5]. Treatment for symptomatic pilonidal sinus involves surgery to incise and drain the abscess. The surgery can be either wide excision and healing by secondary intention (longer healing time, low chance of recurrence), excision and primary closure by sutures (quicker healing, high risk of recurrence), or plastic surgical technique (for recurring and/or extensive sinus). The other procedures include topical application of natural polyphenols/laser epilation [3].

Scalp pilonidal sinus is a rare variant of pilonidal sinus. In most cases, its etiology remains unknown [2] [6] [7][10]. In some reported cases, trauma was accounted for the etiology by their authors [11] [12] [13]. Our patient did not report head trauma. Pilonidal sinus typically occurs in the sacrococcygeal area [2]. However, it may appear in other areas like axilla, groin, interdigital web, umbilicus, nose, suprapubic area, clitoris, prepuce, or penis [3]. Scalp pilonidal sinus is very rare. Table 1 gives scalp pilonidal sinus literature review with localization and proposed etiology.

Although extremely rare, pilonidal sinus may occur in the scalp. Its etiology remains unknown. It can be excised and primarily sutured using local anesthesia.

1. Clothier PR, Haywood IR. The natural history of the post anal (pilonidal) sinus. Ann R Coll Surg Engl 1984 May;66(3):201–3.   [Pubmed]    
2. Chopade AB, Shojai AR, Jadhav R, Yadav V. Pilonidal sinus over a rare site. IJSR 2015;4:(2).   [CrossRef]    
3. Sunkara A, Wagh D, Harode S. Intermammary pilonidal sinus. Int J Trichology 2010 Jul;2(2):116–8.   [CrossRef]   [Pubmed]    
4. Søndenaa K, Andersen E, Nesvik I, Søreide JA. Patient characteristics and symptoms in chronic pilonidal sinus disease. Int J Colorectal Dis 1995;10(1):39–42.   [CrossRef]   [Pubmed]    
5. Yavalkar P, Shelke R. Intermammary Pilonidal Sinus: A Case Report. Indian Journal of Medical Case Reports 2014;3(2):20–2.    
6. Pehlivanli F, Karaca G, Pekcici MR, Yildirim K, Karaca B. Pilonidal sinus disease of the scalp. Am Surg 2012 Apr;78(4):E242–3.   [Pubmed]    
7. Olcay Nalbant Ak, Nalbant E. Pilonidal Sinus of the Scalp: a Case Report and Review of the Literature. Balkan Med J 2011;28:445–7.   [CrossRef]    
8. Bascom J. Pilonidal disease: long-term results of follicle removal. Dis Colon Rectum 1983 Dec;26(12):800–7.   [CrossRef]   [Pubmed]    
9. Chintapatla S, Safarani N, Kumar S, Haboubi N. Sacrococcygeal pilonidal sinus: historical review, pathological insight and surgical options. Tech Coloproctol 2003 Apr;7(1):3–8.   [Pubmed]    
10. Yokoyama T, Nishimura K, Hakamada A, et al. Pilonidal sinus of the supra-auricle area. J Eur Acad Dermatol Venereol 2007 Feb;21(2):257–8.   [Pubmed]    
11. Chiu MW, Abrishami P, Sadeghi P. Letter: pilonidal cyst of the scalp. Dermatol Surg 2008 Sep;34(9):1294–5.   [CrossRef]   [Pubmed]    
12. Kosaka M, Kida M, Mori H, Kamiishi H. Pilonidal cyst of the scalp due to single minor trauma. Dermatol Surg 2007 Apr;33(4):505–7.   [CrossRef]   [Pubmed]    
13. Moyer DG. Pilonidal cyst of the scalp. Arch Dermatol 1972 Apr;105(4):578–9.   [CrossRef]   [Pubmed]