To the Editor,We read with interest the excellent article titled "Use of dermoscopy in the diagnosis of
temporal triangular alopecia" by Campos et al.[1] However, we take issue with their
statement that the incidence of congenital triangular alopecia has been estimated at
0.11%.[2] Taken at face value,
readers may assume that 0.11% of the general population have congenital triangular
alopecia. The 0.11% number was derived from the study by Garcia-Hernandez et
al. They reviewed 6,200 randomly selected patients seen for the first time
at a dermatology clinic at the Virgen Macarena University Hospital in Spain, and found
that 7 (0.11%) patients had congenital triangular alopecia.[2] We would like to point out that the population studied
was highly selective and did not represent the true incidence among the general
population.Congenital triangular alopecia was first described in 1905 by Raymond Sabouraud in his
book "Manuel elementaire de dermatologie topographique regionale" as "alopecia
triangulaire congenitale de la temp."[3]
Li et al. identified only 126 cases of congenital triangular alopecia
in the published literature, cited on Pubmed between 1905 and 2015.[4] Patients may not seek medical attention
for this benign and asymptomatic lesion, while many may be undiagnosed or misdiagnosed.
Both factors could explain the scarcity of reported cases. We are under the impression
that congenital triangular alopecia is more common than currently appreciated. With
increased awareness of this condition, many more cases will conceivably be reported.Recently, a 3-year-old Chinese girl presented to us with an 18-month history of a
localized triangular area of hair loss in the right frontotemporal area. We searched in
the literature but could not find the incidence of congenital triangular alopecia in the
general population. It is hoped that properly designed studies will better elucidate the
incidence of congenital triangular alopecia in the general population.