Temporal Triangular Alopecia

Temporal triangular alopecia (congenital triangular alopecia, Brauer naevus) is a non-scarring, non-progressive patch of hair loss in the frontotemporal scalp, usually triangular or oval, that contains vellus hairs.

It is present from birth but is typically noticed between 2 and 9 years of age, when terminal hair should have replaced the vellus hair. It affects both sexes, is unilateral in about 80% of patients and bilateral in the rest.

The patch persists for life and does not extend. The cause is unknown, and it may be a form of mosaicism.

Pathophysiology.

Hair follicles are present but are miniaturised, so only vellus hairs grow. The area is a form of hair follicle hypoplasia or naevus. No inflammation or scarring is found.

• A well defined triangular, oval or lancet shaped patch of 2 to 4 cm, 1 to 2 cm behind the frontal hairline in the temporal area, with fine, short vellus hair, and normal skin.
• No symptoms or associated skin disease. It is more often left sided.
• Associated with other abnormalities rarely (for example Down syndrome and congenital heart disease have been reported).

• Clinical diagnosis from the age at onset, site and persistence.
• Trichoscopy: numerous vellus hairs with normal follicular openings, and no scarring features, broken hairs or exclamation mark hairs.
• Biopsy is rarely needed: normal number of follicles with a reduced proportion of terminal hairs.

Differential diagnosis.

• Alopecia areata (exclamation mark hairs, yellow dots) and trichotillomania.
• Traction alopecia, aplasia cutis congenita and tinea capitis.
• Lichen planopilaris, frontal fibrosing alopecia and neonatal occipital alopecia.

• Reassure the family that the condition is benign and non-progressive. No medical treatment restores the hair.
• Topical minoxidil 5% has uncertain benefit and relapse on stopping is usual.
• Surgery in late childhood or adolescence if desired: excision of the patch (with closure by direct suture) or hair transplantation (follicular unit grafts) with good results in most patients.
• Hairstyling and camouflage products.

Monitoring. No routine review.

Referral and escalation. Dermatology or plastic surgery for patients wanting treatment.