The patient was given a diagnosis of widespread tinea corporis. This diagnosis may not fit with the common paradigm of tinea as thin, scaly annular patches, often known as ringworm. However, a skin scraping was performed on the red scaly patches, and the diagnosis was confirmed.
A skin scraping is a simple procedure that takes minutes to yield actionable information. A scalpel blade is used in a scraping motion and skin flakes are caught on a slide as they fall from the skin. (Another glass slide can be used in place of the scalpel, which is slightly less frightening for children.) The sample is then covered with 1 to 2 drops of potassium hydroxide (KOH), in 1 of various available formulations, and covered with a coverslip. Gently heating the slide, or simply waiting a few minutes, will allow the KOH to begin dissolving some keratinocyte membranes and stain any fungal walls light purple.
Hyphae, which may be linear (see Figure) or branched, will cross multiple cell membranes and are themselves about the thickness of a cell membrane. A high-powered view of hyphae should reveal nuclei and septa.
Skin biopsy, culture, and a skin scraping sent to an outside lab are all alternatives to the aforementioned approach but take days or weeks to yield a result. Fungal polymerase chain reaction is a novel diagnostic approach that can be both sensitive and specific, but still requires several days for results and incurs additional cost to the patient.
In this case, the diagnosis was made at the patient’s bedside and terbinafine 250 mg/d for 3 weeks was chosen as systemic therapy because of the extent of disease. At the follow-up visit 2 months later, the patient’s rash had completely cleared.
Text and photos courtesy of Jonathan Karnes, MD, medical director, MDFMR Dermatology Services, Augusta, ME. (Photo copyright retained.)