Tinea and fungal skin infection

Overview & Definition

Picture the seven-year-old who itches at an expanding pink ring on her forearm. The edge is raised and scaly, the centre has cleared, and over two weeks it has slowly grown outward. This is tinea corporis, the archetypal ringworm lesion, and the pattern of an active advancing border with central clearing is the single most useful clue that a scaly patch is fungal rather than eczema or psoriasis. [6]

Now picture a different child: a four-year-old with a patch of hair loss and broken-off stubs on his scalp, a little scaly, with a firm lump of enlarged nodes at the back of his neck. The hair loss is not alopecia areata, and the lump is not a bacterial abscess — this is tinea capitis, the one dermatophyte infection that lives inside the hair shaft and that a cream can never reach. [1]

Tinea, also called dermatophytosis or ringworm, is a superficial infection of keratinised tissue — the stratum corneum, the hair shaft and the nail plate — by a small group of fungi called dermatophytes. They belong to three genera: Trichophyton, Microsporum and Epidermophyton. Dermatophytes digest keratin using secreted keratinases, so they live in dead keratinised tissue and do not invade living skin, which is why the disease stays superficial but keeps spreading outward across the skin surface. The name ringworm describes the expanding annular lesion and has nothing to do with a worm. [1] [6]

Three ideas anchor the whole topic for a fellowship candidate. First, the site decides the name and the treatment: scalp disease is capitis and always needs tablets, whereas body and groin disease usually needs only a cream. Second, the infecting species guides the drug: terbinafine works better for Trichophyton and griseofulvin better for Microsporum. Third, this is a contagious household and community problem: untreated carriers, siblings, classmates and pets keep reinfecting the child, so curing one child often means looking at the whole family. [2] [3]