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Ultraviolet Dermoscopy for Diagnosis and Treatment Monitoring of Ectothrix Tinea Capitis Caused by Microsporum canis

Tae-Jong Kang,Kyung-Hwa Nam,Seok-Kweon Yun,Jin Park
10.17966/JMI.2024.29.1.39 Epub 2024 March 28

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Abstract



Keywords



Dermatophytes Dermoscopy Microsporum canis Tinea capitis Ultraviolet dermoscopy



An 82-year-old woman with hypertension presented with a 6-month history of a pruritic hair loss patch on her right parietal scalp; she had a history of close contact with a dog. Physical examination revealed numerous red-brown alopecia patches with thick, adherent scales and crusted papules (Fig. 1A). Dermoscopy revealed black dots, short broken hair with diffuse erythema, and perifollicular scales (Fig. 1B). Further- more, ultraviolet (UV) dermoscopy (wavelength: 365 nm; Dermlite DL5, 3Gen LLC, CA, USA) revealed bright white-blue fluorescence on infected broken hair (Fig. 1C). Fungal culture and polymerase chain reaction of scalp samples identified Microsporum canis as the causative agent for tinea capitis (TC). Subsequent oral terbinafine (250 mg/day) and topical isoconazole treatment completely cured the lesions; moreover, hair regrowth without fluorescence was observed (Fig. 1D, 1E).

Ectothrix TC, caused by M. canis, is characterized by accu- mulation of hyphae and spores around the outside of the hair shaft1. In ectothrix-type invasion, infected hair exhibit yellow-green fluorescence under Wood lamp examination. Simple, noninvasive dermoscopy is a useful bedside tool for TC diag- nosis and causative species prediction. Straight broken hair, such as Morse code-like and zigzag hair, are highly suggestive of M. canis-induced ectothrix TC2. Compared with standard dermoscopy, UV dermoscopy, which combines polarized and UV light, can effectively detect infected hairs3, and help in accurate diagnosis and treatment response monitoring of TC caused by M. canis.

Figure 1. (A) Localized red-brown alopecic patches with thick, adherent scales and crusted papules on the right parietal scalp (B) Dermoscopic findings showing black dots, short broken hair, Morse code-like hairs (black arrow), zigzag hairs (red arrow), diffuse erythema, and scales (polarized, ×10) (C) Ultraviolet dermoscopy revealing bright white-blue fluores- cence of the infected, broken hairs (red arrowhead) and zigzag hairs (red arrow) (ultraviolet mode, ×10) (D, E) After 3 months of follow-up, short regrowing upright or circle hair (black arrowhead) were observed without any broken hairs. Ultraviolet dermoscopy revealed no fluorescence (polarized and ultraviolet mode, ×10).


References


1. Craddock LN, Schieke SM. Superficial fungal infection. In Kang S, Amagai M, Bruckner AL, Enk AH, Margolis DJ, McMichael AJ, et al. editors. In: Fitzpatrick's Dermatology, 9th ed. New York: McGraw-Hill, 2019:2941-2944

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3. Tang J, Ran X, Ran Y. Ultraviolet dermoscopy for the diagnosis of tinea capitis. J Am Acad Dermatol 2017;76: S28-S30
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