Unusual Presentation of Hertoghe’s Sign and Its Trichoscopic Features

Case Presentation

A 21-year-old man with a history of late-onset atopic dermatitis at the age of 15 reported a prominent flare-up of the disease for the past three months and noted eyebrow thinning during this period. In addition to the clinical signs characteristic of atopic dermatitis, physical examination revealed unilateral hair thinning involving the entire eyebrow (Figure 1). No shedding or complete hair loss was found in other parts of the body. The patient had no history of alopecia areata, seborrheic dermatitis, or infection. Despite the affected area being notably pruritic, he denied rubbing or scratching it. We performed laboratory tests to rule out hypothyroidism.

Figure 1.

(A) Significant difference in the number of hair shafts between the affected and unaffected eyebrows. (B,C,D) trichoscopic images of affected eyebrow: diffuse erythema, scaling (yellow ring), monilethrix-like hairs (black arrows), black dots (white rings), empty hair follicles (black rings), pili torti (green arrows), hairs broken at different lengths (green rings), micro-exclamation mark hair (blue arrow).

Hair thinning limited to the lateral one-third of both eyebrows is known as Hertoghe’s sign. It is predominantly observed in atopic dermatitis and hypothyroidism [1]. There are no disease-specific trichoscopic features documented for this condition. In our case, trichoscopy of the affected eyebrow showed: decreased number of terminal hairs, diffuse erythema, scaling, monilethrix-like hairs, pili torti, hairs broken at different lengths, black dots, micro-exclamation mark hairs, and empty hair follicles.

Teaching Point

If a physician encounters isolated loss of eyebrow as a standalone condition, it is essential to consider Hertoghe’s sign as a differential diagnosis, making a detailed description of all trichoscopic findings much more important. Our patient had an unusual presentation of this sign - unilateral hair thinning involving the entire eyebrow, rather than the typical presentation, which is limited to the lateral one-third [2].