Dear Sir,

A 23-day-old full-term male infant was brought to the dermatology outpatient department with a complaint of greenish-blue patches on the left side of face and lower back since birth. No history of any topical application to the affected area or child abuse could be elicited. Birth history and maternal history were unremarkable. Physical examination revealed faint blue to green-colored grayish macules distributed over the left side of the cheek along the distribution of the ophthalmic and maxillary branch of the trigeminal nerve as well as the posterior aspect of lower trunk [Figures 1 and 2]. The pigment was uniformly present over the affected region while the sclera did not show any pigmentation. The rest of the mucocutaneous examination was normal. A complete physical examination was carried out and did not reveal any other congenital anomalies. The routine blood and urine investigations were reportedly normal. As consent for biopsy could not be obtained, a clinical diagnosis of an aberrant Mongolian spot was made. No active treatment was done, and the patient was advised to follow up regularly to observe the expected resolution.

Figure 1:: Bluish-green macules seen over the left side of the cheek along the distribution of ophthalmic and maxillary branches of the trigeminal nerve.

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Figure 2:: Bluish-green macules seen over the lower aspect of the posterior trunk.

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Dermal melanocytosis occurs due to the arrest of migration of melanocytes during fetal life imparting a blue to slate gray hue due to tyndallization. It commonly presents as circumscribed greenish-blue to gray macules over the midline, especially the lumbosacral region, known as Mongolian spots which usually regress by early childhood.[1] Extrasacral Mongolian spots are rare and are referred to as aberrant Mongolian spots.

Leung et al. and Reza et al. observed the sacral area to be the most commonly affected site with none over head and neck.[1,2] Park et al. also reported a case of extensive aberrant Mongolian spot which spared face and scalp.[3] However Morooka et al. described 3 cases of Mongolian spots over face which were later labeled as nevus of Ota by Hidano.[4] Recently Leung et al. and Tanyasiri et al. reported the facial presence of Mongolian spots along the areas supplied by maxillary and mandibular branch of trigeminal nerve respectively.[5,6] Notably, nevus of Ota is a very close differential of aberrant Mongolian spot of face which is distinguished by hyperigmentation of sclera in addition to the facial regions supplied by trigeminal nerve.

Our case is unique as the presence of an aberrant Mongolian spot on the face in the region innervated by the ophthalmic branch of the trigeminal nerve with sacral presentation is hitherto unreported to the best of our knowledge. It also presses the need to differentiate it from similar types of dermal melanocytosis.