Congenital Triangular Alopecia

Congenital triangular alopecia, also known as temporal triangular alopecia or Brauer nevus, is a benign, nonprogressive, and non-scarring form of alopecia that typically presents as triangular, oval, or lancet-shaped patches of hair loss on the frontotemporal scalp, though it can also occur over the parietal area and vertex. The condition is usually noticed in children between 2 and 4 years of age but can be present at birth or develop in adulthood. Its exact incidence is unknown, and it is often underdiagnosed or misdiagnosed due to its benign nature. The etiology is unclear, but it may be related to mosaicism and could be a paradominant trait. Diagnosis is based on history, clinical features, and typical location, and it can be distinguished from other types of alopecia using dermatoscopy, which reveals a carpet of short vellus hairs and normal follicular openings without the diagnostic features of other localized alopecias. Histopathology confirms the presence of normal numbers of hair follicles and miniaturized telogen hairs without scarring or perifollicular inflammation.