Temporal triangular alopecia and a review of 52 past cases.

Temporal triangular alopecia (TTA) is a circumscribed, non-cicatricial form of alopecia confined to the frontotemporal region. The patient, a 15-year-old boy, was noticed at birth to have an alopecial area, sized 1.5 cm x 2.5 cm, in the right temporal region. Microscopic examination revealed miniaturized hair follicles accompanied by differentiated sebaceous glands. We have provided a synopsis of the past 52 cases. Of the 53 cases of TTA including our case, more than half (55.8%) were detected in childhood between the ages of 2 and 9 years, while 36.5% were detected at birth and only 3.8% (only two cases) in adulthood. There were three familial cases. Several congenital diseases were associated with the condition, for example, phakomatosis pigmentovascularis, Down syndrome and Dandy-Walker malformation. This information suggests that TTA can be recognized as a hamartomatous mosaic disease.