Tinea corporis, cruris and pedis

ringworm · tinea · tinea corporis · tinea cruris · athlete's foot · tinea pedis · jock itch · fungal skin infection

An itchy annular scaly plaque with an active edge - and the interdigital kind is the portal of entry for recurrent cellulitis.

GPBand C

Red flags

Extensive or rapidly spreading disease, or failure to respond to appropriate antifungal treatment
Immunosuppression or poorly controlled diabetes
Scalp or beard involvement - needs oral treatment, topical will not clear it
Concurrent cellulitis with interdigital tinea - treat both, or the cellulitis recurs
Widespread tinea in a young person with no obvious cause - consider undiagnosed immunosuppression

Recognise

On light skin

Annular pink-red plaque with a raised scaly advancing edge and central clearing, itchy, enlarging slowly.

On brown and black skin

The ring may appear grey, dark brown, violaceous or simply hyperpigmented rather than pink, and the central clearing can be much less obvious, so the classic ring is often not seen. The scale and the palpable raised active edge are the tone-independent findings - look obliquely across the skin for scale and run a finger over the border. Tinea in brown and black skin is frequently misdiagnosed as eczema and treated with a topical steroid, which produces tinea incognito: the scale and the edge disappear, the rash spreads, and the true diagnosis is obscured. Post-inflammatory hyperpigmentation after successful treatment is common and does not mean failure.

In any skin tone

A raised, scaly, active edge with relative central clearing
Itchy, and usually asymmetrical or unilateral - unlike eczema and psoriasis
Slowly enlarging over weeks
Check the feet and the toe webs in every patient with cellulitis - interdigital tinea is a common portal of entry
A history of a steroid cream that made it worse, or made it better then worse - suspect tinea incognito

Distribution

Tinea corporis anywhere on the trunk or limbs; tinea cruris in the groin, usually sparing the scrotum; tinea pedis between the toes, particularly the fourth web space, or as a dry scaling moccasin pattern on the sole.

Photographs

Tinea corporis on dark skin. Discrete rings with a raised, grey-white scaly edge and a clear centre. There is no red ring at all. The edge i — Tinea corporis on dark skin. **Discrete rings with a raised, grey-white scaly edge and a clear centre.** There is no red ring at all. The edge is what you look at and what you scrape - its scale is both the diagnosis and the specimen.
Fitzpatrick IV-VI (Fitzpatrick type estimated from the photograph, not stated by the source) · Oladokun RE, Lehloenya RJ, Hlela C, Ubesie AC, Katibi SO, Malande OO, Eley BS · Atlas of Paediatric HIV Infection, UCT Libraries Press 2018 - Chapter 3: Fungal Skin Infections, p53 · CC BY 4.0

Widespread tinea of the face, arm and trunk. The plaques are scaly and advancing at the margin with flatter centres; on the cheek the ring h — Widespread tinea of the face, arm and trunk. The plaques are **scaly and advancing at the margin with flatter centres**; on the cheek the ring has broken up into an irregular, confluent plaque, which is the pattern that gets treated as eczema for months. Facial tinea in particular is routinely given a topical steroid, which removes the scale and makes the ring harder to see.
Fitzpatrick IV (Fitzpatrick type estimated from the photograph, not stated by the source) · Oladokun RE, Lehloenya RJ, Hlela C, Ubesie AC, Katibi SO, Malande OO, Eley BS · Atlas of Paediatric HIV Infection, UCT Libraries Press 2018 - Chapter 3: Fungal Skin Infections, p54 · CC BY 4.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Atopic eczema and infected eczema — The commonest misdiagnosis in both directions. Eczema is symmetrical and has no active scaly edge; treating tinea with steroid produces tinea incognito
Tinea capitis and kerion — Scalp disease needs oral treatment and is a different management problem
Cutaneous candidiasis — Candida involves the folds with satellite lesions; tinea cruris spares the scrotum and has an active edge
Cellulitis — Not a mimic - a consequence. Interdigital tinea is a portal of entry for recurrent lower-limb cellulitis
Granuloma annulare — The mistake that actually happens. Both are annular with a raised edge, but granuloma annulare has no scale and does not itch - months of antifungal for it is a common history
Pityriasis versicolor — Both are superficial fungal infections that scale, but versicolor gives confluent macules on the upper trunk rather than an advancing annular edge

What to do in the ED

Treat with a topical antifungal, following local policy on the preparation. In an adult, oral treatment is for severe or extensive disease and CKS ties it to sampling - a positive mycology result, a strong clinical suspicion before results are back, or a negative result with strongly suggestive features plus repeat sampling. In a child with severe or extensive disease, CKS arranges referral to a paediatric dermatologist rather than oral treatment in primary care. Scalp and nail disease needs oral therapy either way
Do not prescribe a topical steroid or a combined steroid-antifungal on the assumption it is eczema where the edge is scaly and active
Examine the toe webs, and treat interdigital tinea in anyone presenting with lower-limb cellulitis
Take skin scrapings for mycology before committing to an oral course - CKS makes sampling part of that decision rather than optional - and also where the diagnosis is uncertain or topical treatment has failed
Advise on reducing recurrence: dry thoroughly between the toes, change socks, avoid sharing towels, treat footwear
Look for and treat other sites in the same patient, including nails, since untreated nail disease reinfects the skin

Disposition

Topical treatment and discharge with GP follow-up. Refer for mycology and oral treatment where extensive, resistant, or involving scalp or nails.

Safety-netting

Use the antifungal cream exactly as the product directs, including continuing for the period stated after the skin looks normal - stopping as soon as it looks better is the usual reason it comes back. Return if it spreads, if it is no better by the end of the course the product specifies, or if the skin becomes hot, painful, swollen or you develop a fever. Stay away from nursery, school or communal areas until treatment has started, and then attend as normal. Do not use a steroid cream on it unless a doctor has told you to - it can make it spread and hide it. Darker marks left behind afterwards will fade.

Sources

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