A 12-year-old girl presented with asymptomatic skin lesions over the left side of the face, which were present since birth. At birth, the lesions were limited to the mandibular region only but they increased in number with advancing age to involve the whole left side of the face. Lesion had stopped growing a year ago. Cutaneous examination revealed multiple irregular honeycomb like pitted scars. Scattered comedones were present within these pitted scars. The lesions were present over the left side of face only extending from mandibular region to upper part of the forehead sharply demarcated at midline, ranging in size from a few millimeters to a few centimeters.(Figs. 1 and 2) There were no such lesions present elsewhere in the body. Hair, nail and mucosae were absolutely normal. Examination of the central nervous system and skeletal system including ophthalmic check-up did not reveal anything abnormal. Family history was non-contributory. Histology showed closely placed dilated follicular ostia with prominent orthokeratotic plugging. The follicular walls were lined by atrophic epithelium composed of a few layers of keratinocytes. Based on the clinical and histopathological findings, a diagnosis of "unilateral facial nevus comedonicus" has been done for our case. She has been prescribed topical retinoic acid and referred for laser treatment, which is best suited for her cosmetic concerns.

(a)	(b)
Fig. 1 (a) Multiple irregular honeycomb like pitted scars with comedones with (b) sharp midline demarcation.

The etiology of nevus comedonicus is unclear. One school of thought considers it to be a hamartoma arising out of improper development of mesodermal part of the folliculosebaceous unit, and subsequent abnormal differentiation of the epithelial portion. Another view is that nevus comedonicus is an epidermal nevus involving hair follicles. Nevus comedonicus may be linear, interrupted, unilateral, bilateral, present in a dermatomal distribution, following the lines of Blaschko, or segmental. Close clinical differential diagnoses include acne vulgaris (starts with comedones and progresses to papule, pustule or nodulocystic type if treatment not done), familial dyskeratotic comedones (family history positive, lesions on trunk and extremities more common), nevus spilus (darker macules or papules in a background of tan macular area) and epidermal nevus (well-circumscribed, hyperpigmented, papillomatous papules or plaques). Asymptomatic lesions may be left untreated or therapy may be individualised absolutely for cosmetic reasons. Some lesions improve with topical retinoic acid, salicylic acid, or ammonium lactate lotion. Laser treatment using carbon dioxide laser or Erbium yag laser may be used.