Nigel Stollery is a GP and dermatology clinical assistant in Kibworth, Leicestershire
Onycholysis may also be caused by trauma. Mycological diagnosis from nail clippings is important as treatment may involve up to three months of oral therapy.
For non-matrix infections topical treatment may be adequate. This need only be applied once a week and comes in a kit with instructions and a nail file.
Parallel longitudinal furrows are often misdiagnosed as fungal infections. They may be seen in alopecia areata, lichen planus, Darier's disease and trauma.
The majority of nail infections are caused
by dermatophytes such as T. rubrum. The second most common cause is the candida species.
A rarer cause of nail infection is Scytalidium, which typically causes a black subungual discolouration. Always remember the potentially fatal differential of this is a subungual melanoma. If in doubt a biopsy may be advisable.
Studies suggest the prevalence of fungal nail infection ranges between 2.71-10 per cent of the population (incidence increasing with age). In many cases reassurance and camouflage may be all that is required.
Where treatment is undertaken with oral antifungals such as terbinafine, the monitoring of liver function tests is a good idea.
Fungal nail infections are almost always preceded by athlete's foot, which may be a simple aid to diagnosis.
When obtaining clippings and subungual debris for culture and microscopy, proximal samples are more likely to improve the chances of detecting viable fungus compared with distal clippings.
When Candida is suspected, a swab dipped in saline and run under the proximal nail fold is a better way of detecting the yeast than by clippings alone.