Triangular alopecia

A rare form of hair loss

Classification
External resources

Triangular alopecia, also known as temporal triangular alopecia or congenital triangular alopecia, is a rare, non-scarring form of hair loss that typically presents in childhood. It is characterized by a well-defined, triangular or oval patch of hair loss, usually located in the temporal region of the scalp.

Presentation

Triangular alopecia is most commonly observed in children, although it can also be diagnosed in adults. The condition is usually unilateral, affecting only one side of the scalp, but bilateral cases have been reported. The affected area is typically devoid of hair, but may contain fine, vellus hairs. The skin in the affected region appears normal, without signs of inflammation or scarring.

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Triangular alopecia in a child

Pathophysiology

The exact cause of triangular alopecia is not well understood. It is believed to be a developmental defect rather than a true form of alopecia. Some studies suggest a possible genetic component, as familial cases have been documented. The condition is not associated with systemic diseases or other dermatological conditions.

Diagnosis

The diagnosis of triangular alopecia is primarily clinical, based on the characteristic appearance of the hair loss. A dermatologist may perform a trichoscopy to examine the hair and scalp more closely. A skin biopsy is rarely necessary but can be performed to rule out other causes of hair loss. The biopsy would typically show a normal number of hair follicles, with a predominance of vellus hairs.

Treatment

Treatment options for triangular alopecia are limited. In some cases, topical minoxidil may be used to stimulate hair growth, although its effectiveness is variable. Surgical options, such as hair transplantation, can be considered for cosmetic reasons, especially in older children and adults. The decision to treat is often based on the psychological impact of the condition on the patient.

Prognosis

Triangular alopecia is a benign condition with no associated health risks. The hair loss is permanent, but it does not progress beyond the initial area. The prognosis is excellent in terms of overall health, but the cosmetic appearance can be distressing for some individuals.

Genetics

While the majority of cases are sporadic, there is evidence to suggest a genetic component in some instances. The condition has been observed in multiple members of the same family, suggesting an autosomal dominant pattern of inheritance.

Autosomal dominant inheritance pattern

Related pages

• Alopecia areata
• Androgenetic alopecia
• Scarring alopecia