Congenital Triangular Alopecia: A Close Mimicker of Alopecia Areata

Sir,

A 13-year-old male child presented with a localized area of hair loss over the left fronto-temporal region since the age of 3 years. The patch had remained persistent since its appearance. There was no history of any trauma or absence of skin at the site of alopecia at birth. None of the family members had similar hair loss. The patient had been treated in the past with topical and intra-lesional steroid by various dermatologists as a case of alopecia areata without any improvement. Examination revealed a 2.0×2.5 cm patch of non-scarring alopecia over the left fronto-temporal region with its apex toward the vertex [Figure 1]. A few vellus hair were present in the patch. There was no scaling or erythema in the lesion. Relative fixity of the patch, triangular shape of alopecia, absence of exclamation hair and lack of response to any treatment in past led us to the diagnosis of congenital triangular alopecia. Parents did not give consent for biopsy confirmation. Counseling of the parents was done about the poor prospect of hair regrowth and option of hair transplantation in future.

Figure 1.

Triangular patch of alopecia over the left fronto-temporal region

Congenital triangular alopecia (CTA), also known as temporal triangular alopecia (TTA) or Brauer nevus, is a circumscribed, non-scarring form of alopecia present over the temporal region.[1] CTA was first reported by Sabouraud in 1905.[2] Around 52 cases have been reported so far.[3] It is characterized by triangular or lancet-shaped area of hair loss, usually unilaterally.[3,4] CTA, as its name suggests, is most of the time not congenital, but usually manifests after 2 years of age.[5] It is likely to be noticed by parents only in childhood when the vellus are replaced by terminal hair. It may rarely appear in adulthood as well.[6] Androgenetic alopecia might overlap with this condition and pose diagnostic confusion as the child grows up. The cause of CTA remains unknown. It usually occurs sporadically, but may occur within families as a paradominant trait.[7] Histopathological examination shows normal number of hair follicles, all of which are vellus or indeterminate.[8] There is no specific treatment of this condition. Because CTA involves normal than inflamed skin, it does not respond to topical or intra-lesional steroids.[4] It is very likely for CTA to be missed and erroneously diagnosed as alopecia areata and treated as such inadvertently with steroids leading to their abuse and adverse effects. Hair transplantation can be offered to the patient.[2]

The case is being reported to familiarize clinicians about this rare condition that very closely mimics alopecia areata in order to prevent indiscriminate use of steroids.