Boy Has Had “Bald Spot” Since Birth

ANSWER
The answer is temporal triangular alopecia (choice “d”), an unusual form of permanent hair loss preferentially affecting the exact area depicted in this case.

Alopecia areata (choice “a”) involves localized hair loss. By contrast, this patient never had hair in this area to lose.

Nevus sebaceous (choice “b”) is a congenital hamartoma that is typically hairless; there are no follicles, and the bumpy, rough surface is composed of sebaceous globules.

Cutis aplasia (choice “c”) manifests with hairless lesions, but there is marked aplasia of the skin as well and no surface adnexae, let alone hairs or follicles.

DISCUSSION
Temporal triangular alopecia (TTA) is an unusual type of alopecia. Of unknown origin, it usually affects this area of the scalp—and usually unilaterally. Approximately one-third of TTA patients are born with the condition; the rest develop it in the first two to three years of life. As in this case, it is often wrongly attributed to the use of forceps but has nothing to do with trauma. One school of thought holds that TTA is probably an inherited condition—but others disagree.

TTA was originally known as congenital triangular alopecia. However, when enough cases had been accumulated to accurately determine the nature of the condition, it was realized that TTA is not always congenital or triangular. Thus, a new name was bestowed.

The hallmark of TTA is the normal number of hair follicles that only grow vellus hairs. The solitary peripheral tuft of terminal dark hairs is typical of TTA and thus a confirmatory finding.

TREATMENT/PROGNOSIS
TTA is by definition permanent. Since there’s no inflammation (a key difference from alopecia areata), steroids are useless. The only successful treatment for TTA, if any is attempted, is hair transplantation. As of this writing, the family is mulling this treatment option.