- Most common in children
- May result in adenopathy, alopecia or folliculitis.
- Fungal hyphae are seen within the stratum corneum, and invade down the hair follicles.
- Three histologic types exist, depending of the species of dermatophyte: large-spore (5-8 μm) ectothrix, large-spore endothrix and small spore (2-5 μm) ectothrix.
- Fungi may or may not be visible on H&E, and are best seen with GMS or PAS.
- Intraepidermal neutrophils may be present.
- The stratum corneum may show compact orthokeratosis or sometimes the "sandwich sign": ortho- or parakeratosis alternating in layers with the normal basket-weave stratum corneum.
- Epidermal changes can include spongiosis, intraepidermal vesicles or psoriasiform hyperplasia.
- Dermal inflammation can vary from none to a diffuse or perivascular infiltrate of lymphocytes, histiocytes, neutrophils and/or eosinophils.