What is the role of lab testing in the workup of tinea infections?

Updated: Apr 27, 2021
  • Author: Mityanand Ramnarine, MD, FACEP; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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Answer

Direct microscopic examination may be performed. Skin scrapings, nail specimens, or plucked hairs are treated with potassium hydroxide and examined. Hyphae can be visualized in skin and nails. Spores within or around the hair shaft can be detected.

Fungal cultures can be performed for precise identification of the species.

Wood light (UV light) examination may be performed. This examination is used mainly for the diagnosis of tinea capitis. Hairs infected with M audouinii and M canis produce a brilliant yellow-green fluorescence. T schoenleinii causes a dull green fluorescence.

Histology is not needed, but biopsy findings would show spongiosis, parakeratosis (that may alter with orthokeratosis), and a superficial inflammatory infiltrate. Neutrophils may be seen in the stratum corneum, which is a significant diagnostic clue. On occasion, septate branching hyphae are seen in the stratum corneum. Special fungal stains (eg, periodic acid-Schiff, Gomori methenamine silver) may be required.


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