A boy aged 4 years with an unremarkable history presented with progressive alopecia of 3 months’ duration. The physical examination revealed several scaly patches of hair loss with fine scaling in the right temporal and occipital regions (Fig. 1). The mother reported regular contact with stray cats.

Figure 1.

Gray patches of hair loss with fine scaling in the right temporo-occipital region.

The bald areas produced a blue/green fluorescence on the Wood’s lamp test (Fig. 2). Trichoscopy revealed perifollicular scaling and Morse code-like hairs (Fig. 3). The fungal culture confirmed the diagnosis of infection by Microsporum canis.

Figure 2.

Wood’s lamp test showing blue-green fluorescence in hair loss areas, suggestive of ectothrix dermatophyte infection.

Figure 3.

Trichoscopic image showing multiple perifollicular casts (green triangle) and Morse code-like hairs (yellow arrows), characterized by alternating light and dark bands along the hair shaft. These findings are indicative of areas of ectothrix fungal invasion.

Treatment was initiated with oral griseofulvin (20mg/kg/day for 6 weeks) in combination with ketoconazole 2% shampoo.

Tinea capitis is the most common cause of alopecia in childhood. Green fluorescence and characteristic trichoscopic findings, such as Morse code hairs, allow for an immediate identification of ectothrix infection—usually involving a Microsporum species and associated with gray patch lesions—and help differentiate it from trichophytosis, which presents with black dots, negative fluorescence, and corkscrew or zigzag hairs.1–3

Dermoscopy is becoming increasingly available in clinical practice, and there are portable ultraviolet light devices that can be carried like flashlights, facilitating the diagnosis and follow-up of tinea capitis in the primary care setting.