CASE #2: Temporal triangular alopecia
Temporal triangular alopecia (TTA), previously known as congenital triangular alopecia, was initially described in 1905.5 TTA is a nonscarring, noninflammatory alopecia consisting of normal hair density but made up of only vellus hairs. The etiology of TTA is unknown, and rare familial cases have been described.5 The term congenital was misleading because many cases are not apparent at birth; most cases of TTA develop two to six years after birth.5 Lesions that do not develop until adulthood have been reported.6
TTA most commonly presents as triangular or lancet-shaped lesions over the temples that are a few centimeters in width. The lancet is oriented so that the tip points posteriorly and superiorly.2 The lesions appear hairless; however, viewing the lesions under magnification or with dermoscopy reveals fine vellus hairs.2,6 The lesions are most commonly unilateral (80%) but can be bilateral (20%).5 The condition can rarely occur over areas of the scalp other than the temples.2
TTA has been associated with other cutaneous and systemic conditions, including phakomatosis pigmentovascularis, congenital heart disease, bone and teeth abnormalities, multiple lentigines, café-au-lait patches, renal abnormalities, aplasia cutis congenita, mental retardation, epilepsy, and Down syndrome.5
The differential diagnosis of TTA includes AA, trichotillomania, traction alopecia, or aplasia cutis congenita.6 It is not uncommon for TTA to be initially misdiagnosed as AA. The two entities should be easily differentiated by history and view under magnification or dermoscopy. TTA should demonstrate normal follicular openings with vellus hairs, while AA should show normal follicular ostea with no hair, dystrophic hair, or the “exclamation point” hairs discussed previously. Additionally, the presence of yellow dots within the follicular ostea of both empty and hair-bearing follicles is a characteristic feature of AA that is not seen in TTA.6
Both TTA and AA need to be distinguished from trichotillomania (self-induced plucking or breakage of hair). Trichotillomania is often associated with psychological stress or personality disorders. Areas of alopecia characteristically have bizarre geometric shapes with angular borders. The lesions also characteristically contain hair of varying lengths.
If there is uncertainty regarding the diagnosis, a punch biopsy should be performed. Microscopically, TTA reveals normal numbers of follicles, but almost all are vellus hairs. All other features are normal, and there is no inflammation present. The small hair size requires transverse sectioning of the specimen for assessment.2 Decreased follicular density has recently been reported in one biopsy specimen.7
The patches of alopecia in TTA will persist for life. Topical minoxidil has been used in an attempt to regrow terminal hair over these lesions, but there are no reports of its efficacy. Successful treatments for TTA include complete excision of the patch of alopecia or hair restoration surgery using either punch grafts or, more recently, follicular unit grafts.5
The patient presented here had been diagnosed with AA by his pediatrician three months earlier and had been applying a mid-potency topical steroid to the area with no improvement. We explained the diagnosis and discontinued the topical steroids. We discussed the fact that the only treatments for TTA would be surgical in nature. The patient’s mother was not bothered by the lesion and decided to consider intervention once the child was older.
Dr. Doherty is a resident in the Department of Dermatology at Baylor College of Medicine in Houston. He has no relationships to disclose relating to the content of this article.
- James WD, Berger TG, Elston DM. Diseases of the skin appendages. In: Andrews’ Diseases of the Skin: Clinical Dermatology. 10th ed. Philadelphia, Pa.: Saunders-Elsevier; 2006:749-793.
- Sperling LC. Alopecias. In: Bolognia JL, Jorizzo JL, Rapini RP, eds. Dermatology. 2nd ed. Philadelphia, Pa.: Mosby-Elsevier; 2008:531-548.
- Wasserman D, Guzman-Sanchez DA, Scott K, McMichael A. Alopecia areata. Int J Dermatol. 2007;46:121-131.
- Ioffreda MD. Inflammatory diseases of hair follicles, sweat glands, and cartilage. In: Elder DE, Elenitsas R, Johnson BL, Jr, Murphy GF, eds. Lever’s Histopathology of the Skin. 9th ed. Philadelphia, Pa.: Lippincott Williams & Wilkins; 2005:469-512.
- Wu WY, Otberg N, Kang H, et al. Successful treatment of temporal triangular alopecia by hair restoration surgery using follicular unit transplantation. Dermatol Surg. 2009;35:1307-1310.
- Iorizzo M, Pazzaglia M, Starace M, et al. Videodermoscopy: a useful tool for diagnosing congenital triangular alopecia. Pediatr Dermatol. 2008;25:652-654.
- Silva CY, Lenzy YM, Goldberg LJ. Temporal triangular alopecia with decreased follicular density. J Cutan Pathol. 2010;37:597-599.