Derm Case Challenge: Rash on Chest, Buttocks and Toenail Changes in a Middle-Aged Man

Lindsay Irwin, BS; Preeya T. Shah, MD; Richard Harold Flowers IV, MD

Disclosures

September 06, 2022

Discussion

Tinea corporis is a localized cutaneous dermatophyte infection caused by fungal species, namely of the genera Trichophyton, Microsporum, or Epidermophyton. Dermatophyte infections are often diagnosed on the basis of clinical findings; however, the varied presentations and overlapping features with other dermatologic entities may pose a diagnostic dilemma. Dermatophyte infections are classified by body site involvement:

Tinea corporis manifests as erythematous patches or plaques, with a scaly, advancing raised edge and central clearing, as seen in the patient in this case. This was further highlighted on examination of the patient's buttocks and bilateral dorsal feet, with associated thickened and dystrophic toenails (Figure 4). The rash is frequently pruritic, typically spreads centrifugally from the trunk to the extremities, and may be annular.[1] The main methods and modes of transmission of tinea infections involve contact with other persons, animals, surfaces, soil, and objects.[2]

Figure 4.

Potassium hydroxide preparations performed via skin scraping, from the scaly active borders of this patient's rash on the trunk, buttocks, and feet, were examined directly under the microscope, and each revealed refractile, long, smooth, branching hyphae crossing keratinocyte borders. This test is rapid, inexpensive, and noninvasive, and these findings are classic for the diagnosis of tinea. Of note, fungal culture from skin swabs may also be obtained, although positive cultures can take 1-2 weeks to result. Another useful bedside tool is Wood light examination, because tinea corporis and tinea capitis secondary to Microsporum infections may fluoresce a blue-green color.[1]

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