Derm Dx: Sparse hair since birth - Clinical Advisor

Derm Dx: Sparse hair since birth

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  • Temporal triangular alopecia 1_1012 Derm Dx

  • Temporal triangular alopecia 2_1012 Derm Dx

  • Temporal triangular alopecia 3_1012 Derm Dx

A 3-year-old male presents with an area of very sparse hair at the left anterior hairline. His parents state that this abnormality was present at birth, when it was noted that he had normal hair except in the affected area.

There were no complications during pregnancy or in the perinatal period. The child is otherwise healthy and has met all of his developmental targets. A complete skin exam is significant only for a focal area of sparse to absent scalp hair.

Temporal triangular alopecia describes the focal absence of terminal hairs at the frontal-temporal area of the scalp. The area of hair loss is triangular or lancet shaped, with the point of the triangle oriented posteriorly. The area may appear hairless,...

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Temporal triangular alopecia describes the focal absence of terminal hairs at the frontal-temporal area of the scalp. The area of hair loss is triangular or lancet shaped, with the point of the triangle oriented posteriorly. The area may appear hairless, but actually there are vellus hairs present. Vellus hairs are very thin, fine, light-colored hairs, which are best seen under magnification.

Temporal triangular alopecia is usually unilateral, but bilateral cases have been described. It is a lifelong condition and the affected individual will never develop normal terminal hairs in the affected scalp region. 

The majority of cases are isolated, but there have been individual case reports association with mental retardation, colonic polyposis, eye defects and other anomalies including congenital heart disease. 

Temporal triangular alopecia has a characteristic appearance under the microscope. Patients have a normal number of hair follicles, however the follicles are of the vellus type instead of the thicker and darker terminal hairs typically found on normal scalp skin. The scalp skin is otherwise normal, and there is no associated inflammation. 

Diagnosis

The diagnosis is made by the presence of a lancet or triangular shaped patch of alopecia in the fronto-temporal scalp region in an infant or young child. If the diagnosis is in doubt, a scalp biopsy of the affected region will show a normal number of hair follicles; however, the majority will be of the vellus type. 

Alopecia areata is an acquired hair disorder in which lymphocytes attack the hair follicle.  In alopecia areata, the patches of alopecia are completely smooth and hairless, as opposed to temporal triangular alopecia, in which the alopecic patches actually have small vellus hairs. 

In tinea capitis, the affected region may appear alopecic, but scale or inflammation (such as erythema or pustules) is present. 

Traction alopecia occurs almost exclusively in African-Americans, usually females.  It appears as sparse or absent hair along the frontal and temporal hairline. It is due to hairstyles, such as tight braids, that cause excessive tension on the hair root and is not present at birth. 

Treatment

There is no treatment for temporal triangular alopecia. If cosmetically troublesome, patients should be advised to find a hairstyle that camouflages the defect.  

Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.

References

  1. Bolognia J, Jorizzo JL, Rapini RP. ” Chapter 12: Alopecias.” Dermatology. St. Louis, Mo.: Mosby/Elsevier, 2008.
  2. Weedon D, Strutton G, Rubin AI. “Chapter 15: Diseases of cutaneous appendages.” Weedon’s Skin Pathology. Oxford: Churchill Livingstone/Elsevier, 2010.
  3. Schachner LA, Hansen RC. “Chapter 11: Hair disorders.” Pediatric Dermatology. Edinburgh: Mosby/Elsevier, 2010.
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