Tinea

From Ganfyd

Several dermatophyte fungi affect humans and other species. Not to be confused with taenia coli. In general the itchier and more classical the "ringworm", the more likely it is to be a zoonotic infection rather than an anthropophilic species.

Tinea manum - ringworm on the hand - is likely to be due to the Hedgehog species of the fungus, caught by handling a compost heap. the strain of dermatophtye causing Tinea pedis most commonly found in cities is spreading laterally from the trunk roads displacing the rural strain. This might be due to drifting spores, or commuters living out of town.

Aetiology

Dermatophyte fungi are those few which produce enzymes which break down keratin and can therefore digest the outer layer of intact skin.

Clinical

The most obvious problematic distinction is between hand or foot dermatitis and fungal infection:-

• fungal infection is likely in a unilateral condition
• fluorescence under ultraviolet light ("Wood's light") indicates fungi. Practically obtaining a sufficient source of UV is difficult, the small battery-powered fluorescent tubes used for checking banknotes are not bright enough. UV light emitting diodes are becoming available but it has been impractical to equip each GP's desk with a suitable source, as yet 2006.
• culture.
• therapeutic trial - response to treatment is a reasonable indicator in practice

Investigations

Successful diagnosis of dermatophyte infection by fungal culture requires scraping scales or substantial portions of nail material. Not scraping hard enough is common leading to false negatives.

Dissolving the scrapings in Potassium hydroxide leaves the fungal hyphae visible. Culture on suitable media allows the species to be identified. Specific sensitivity testing against antifungal drugs is not generally available

Blood tests

Radiology

Treatment

Medical

• Terbinafine is effective. For nails or extensive infection oral administration is required, for tinea pedis or cruris application of the 1% cream is sufficient.

Surgical

Prevention

Washing the feet, wearing sandals or going barefoot rather than trainers particularly in summer, using anti-fungal foot powder in boots and shoes, applying surgical spirit to the skin in areas liable to be affected after washing to dry and toughen it.

Post exposure prophylaxis

Notification

External links

• HPA fungal infections page
• How should fungal nail infection be treated? (DTB article).^[1]

Ringworm

• Ringworm patient factsheet from Cumbria and Lancashire Health Protection Unit
• NHS Direct page on ringworm
• Patient UK patient leaflet on ringworm
• Medline Plus medical encyclopedia on ringworm

References