What is the role of skin biopsy in the diagnosis of tinea capitis (scalp ringworm)?

Updated: Feb 21, 2020
  • Author: Marc Zachary Handler, MD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Skin biopsy with particular emphasis on examination of infected hairs with special histochemical stains aids in the identification of the causative fungus, especially in cases of fungal folliculitis (Majocchi granuloma) and onychomycosis. Bullous tinea demonstrates subepidermal edema and reticular degeneration of the epidermis. Tinea corporis demonstrates subacute and chronic dermatitis with or without follicular inflammation and destruction. Suppurative folliculitis may be present. In the mildest form, hyperkeratosis, parakeratosis, spongiosis, slight vasodilatation, and a perivascular inflammatory infiltrate in the upper dermis are present. Fungal hyphae can be demonstrated using routine hematoxylin and eosin stain, and identification can be facilitated by using special stains. Periodic acid-Schiff stain with diastase digestion or counterstained with green dye facilitates identification of fungal elements. See the image below.

Photomicrograph depicting an endoectothrix invasio Photomicrograph depicting an endoectothrix invasion of a hair shaft by Microsporum audouinii. Intrapilary hyphae and spores around the hair shaft are seen (hematoxylin and eosin stain with Periodic acid-Schiff counterstain, magnification X 250).

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