Zeitschrift für medizinische und chirurgische Pathologie
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Congenital Triangular Alopecia Indicating Underlying Disorders

Riddhish T. Sheth, Shivang T. Sheth

Congenital Triangular Alopecia (CTA), also known as temporal triangular alopecia or Brauer nevus, is a non-cicatricial pattern of hair loss that can present at birth, in infancy, or later in life. The condition typically affects the frontotemporal region of the scalp and presents as a non-progressive triangular, or lancet shaped patch of alopecia. The exact etiology of CTA is unknown, though it was once considered to be congenital. It appears to be sporadically acquired in most individuals; however, there have been a small number of familial cases. It is postulated that CTA may reflect mosaicism and may be inherited as a para-dominant trait where a postzygotic loss of the wild type allele in a heterozygote state leads to disease. Others have suggested that CTA may be an ectodermal defect and should be included in the group of epidermal nevi, though no consensus has been reached. The estimated incidence in the general population is 0.11%. The disease histologically presents as replacement of normal hair follicles with sparse vellus hair follicles. The total number of hair follicles is usually within the normal range. There is no evidence of inflammatory infiltrate and the epidermis and dermis are unremarkable. Hair follicles are miniaturized with an increased proportion of vellus or intermediate hairs. CTA is associated with other conditions and it can be a useful signal to clinicians to look for other disorders that may be present in the patient. CTA has been associated with bone abnormalities, café-au-lait patches, congenital heart defects such as atrial septal defects and mitral regurgitation, Down syndrome, Dandy-Walker malformation, and phakomatosis pigmentovascularis. These are a few of the many conditions associated with CTA. When concerned parents bring their child to their clinician for temporal balding, this may help prompt a more detailed examination of the infant to search for associated conditions.