Triangular temporal alopecia

Author: Dr Delwyn Dyall-Smith, Dermatologist, Wagga Wagga, NSW, Australia. DermNet New Zealand Editor in Chief: Adjunct Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. August 2018.


What is triangular temporal alopecia?

Triangular temporal alopecia, also known as congenital temporal alopecia, is a non-scarring form of hair loss usually seen on the frontotemporal scalp.

Triangular alopecia

What causes triangular temporal alopecia?

The cause of triangular temporal alopecia is unknown. It is usually sporadic but has been reported to run in families, suggesting a possible genetic link. Triangular temporal alopecia has been reported in a number of genetic conditions including Down syndrome and phakomatosis pigmentovascularis.

Who is affected by triangular temporal alopecia?

Triangular temporal alopecia most commonly presents in children aged 2–9 years, although it can be present at birth or may first appear in adult life. It affects both men and women and is more commonly seen in light-skinned people.

How common is triangular temporal alopecia?

A survey of 6200 patients attending a dermatology clinic found an incidence of 0.11%. However, this does not necessarily reflect the general population. Many believe the condition is under-reported due to those affected not presenting with symptoms. Misdiagnosis as alopecia areata, male pattern alopecia, traction alopecia, trichotillomania, or congenital aplasia cutis would also contribute to the impression of rarity.

What are the symptoms and signs of triangular temporal alopecia?

Triangular temporal alopecia appears as a triangular or spear-shaped loss of hair, with the ‘point’ of the triangle directed up and back. The shape is sometimes round or oval. It usually does not cause any symptoms, but sometimes patients report dysaesthesia in the lesion.

The lesion most commonly appears on the temporal scalp usually on one side only, although can affect both sides. Involvement of the occipital hairline has also been reported.

Temporal triangular alopecia often has a fringe of terminal hairs along the frontal hairline and sometimes also a tuft within the lesion. Vellus hairs are seen throughout the area.

The lesion remains unchanged throughout life. Despite the presence of vellus hairs, there is no hair regrowth. There are no clinical signs of inflammation or scarring.

How is triangular temporal alopecia diagnosed?

The diagnosis of triangular temporal alopecia is usually clinical.

Dermoscopy can distinguish triangular temporal alopecia from alopecia areata and male pattern alopecia. The dermoscopic features to look for are the presence of vellus hairs throughout the lesion with terminal hairs at the edge. There is no inflammation or scarring. The ‘exclamation mark’ hairs, yellow dots, and black dots of alopecia areata are not present, nor are the streamers of male pattern alopecia.

A skin biopsy is not usually required, but histology shows a normal number of hair follicles in the superficial dermis, mainly of the vellus type.

Suggested criteria for diagnosis include:

  • Triangular or spear-shaped hair loss involving the frontotemporal scalp
  • Dermoscopy revealing normal follicle openings with vellus hairs surrounded by normal terminal hairs
  • Dermoscopy showing no yellow and black dots, dystrophic hairs, or decreased follicular openings
  • No significant hair regrowth after confirming the presence of vellus hairs.

What is the treatment of triangular temporal alopecia?

Treatment is generally not required and is mostly ineffective.

Surgical excision of the lesion, if the lesion is small, or hair transplants, if cosmetically significant, have been used successfully.

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References

1. Campos J, Oliveira C, Romero S et al. Use of dermoscopy in the diagnosis of temporal triangular alopecia. An Bras Dermatol 2015; 90: 123–5. PubMed

2. Jutla S, Patel V, Rajpara A. Triangular temporal alopecia: a rare case in adulthood. Dermatology Online Journal 2016; 22: 19. PubMed

3. Fernandez-Crehuet P, Vano-Galvan S, Martorell-Calatayud A et al. Clinical and trichoscopic characteristics of temporal triangular alopecia: A multicenter study. JAAD 2016; 75: 634–37. PubMed

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