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Description
A 4-year-old Caucasian girl presented with a 1-year history of asymptomatic, localised alopecia. Examination revealed a 3.5×3.0 cm area of alopecia over the right frontotemporal region of the scalp, with its apex towards the vertex (figure 1). There was no scaling or erythema. Her father had a history of extensive androgenetic alopecia. Dermatoscopy of the scalp showed the presence of a ‘carpet’ of vellus hair over the area of interest (figure 2).
The girl suffered from congenital triangular alopecia, also known as temporal triangular alopecia, a circumscribed, non-cicatricial form of alopecia of unknown aetiology.1 It is clinically characterised by a triangular area, confined to one or both frontotemporal regions, in which there is an exclusive presence of vellus hair. It is usually observed in children between 2 and 4 years of age, during the time period in which the remaining scalp demonstrates replacement of vellus hair with terminal hair. Dermatoscopy serves as a useful tool to enhance the diagnostic capability, highlighting the clinical presence of vellus hair2 and allowing differential diagnosis with alopecia areata (showing the presence of dystrophic hairs) and scarring alopecia (showing the absence of hairs and follicles).3 This condition is viewed as permanent with no specific treatment.
Learning points
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Congenital triangular alopecia is a circumscribed, non-cicatricial form of alopecia of unknown aetiology, usually observed in children between 2 and 4 years of age.
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It is clinically characterised by a triangular area, confined to one or both frontotemporal regions, in which there is an exclusive presence of vellus hair.
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Dermatoscopy serves as a useful tool to enhance the diagnostic capability, highlighting the clinical presence of vellus hair.
Footnotes
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Contributors All authors had access to the data and a role in writing the manuscript, and approved the submitted version.
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Competing interests None.
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Patient consent Obtained.
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Provenance and peer review Not commissioned; externally peer reviewed.