Оніхомікоз

Nails have asymptomatic patches of white or yellow discoloration and deformity. There are 3 common characteristic patterns:

• Distal subungual: The nails thicken and yellow, keratin and debris accumulate distally and underneath, and the nail separates from the nail bed (onycholysis).

• Proximal subungual: A form that starts proximally and is a marker of immunosuppression.

• White superficial: A chalky white scale slowly spreads beneath the nail surface.

Onychomycosis of the Great Toes

Сховати деталі

This photo shows onychomycosis of the great toenails. The right toenail shows classic distolateral (a distal subungual) onychomycosis (DLO), whereas the left toenail likely began as DLO and progressed to dermatophytoma (dense collection of hyphae that appears as a linear streak).

Image courtesy of Dr. Edwin P. Ewing, Jr. via the Public Health Image Library of the Centers for Disease Control and Prevention.

• Clinical evaluation

• Potassium hydroxide wet mount examination

• Culture or polymerase chain reaction (PCR)

• Histopathologic examination of periodic acid-Schiff (PAS)–stained nail clippings and subungual debris

(See also an update on the current approaches to diagnosis and treatment of onychomycosis.)

Onychomycosis is suspected by appearance in patients who also have tinea pedis; predictive clinical features include involvement of the 3rd or 5th toenail, involvement of the 1st and 5th toenails on the same foot, and unilateral nail deformity. Subclinical onychomycosis should be considered in patients with recurrent tinea pedis.

Differentiation from psoriasis or lichen planus is important because the therapies differ, so diagnosis is typically confirmed by microscopic examination and, unless microscopic findings are conclusive, culture of scrapings or PCR of clippings. Scrapings are taken from the most proximal position that can be accessed on the affected nail and are examined for hyphae on potassium hydroxide wet mount and cultured. Although more expensive, PCR has become a more common technique to confirm the diagnosis of onychomycosis, especially if cultures are negative or a definitive diagnosis is required (1, 2, 3). Histopathologic examination of PAS–stained nail clippings and subungual debris may also be helpful.

Obtaining an adequate sample of nail for culture can be difficult because the distal subungual debris, which is easy to sample, often does not contain living fungus. Therefore, removing the distal portion of the nail with clippers before sampling or using a small curette to reach more proximally beneath the nail increases the yield.

• Selective use of oral terbinafine or itraconazole

• Occasional use of topical treatments (eg, efinaconazole, tavaborole, ciclopirox 8%, amorolfine)

Onychomycosis is not always treated because many cases are asymptomatic or mild and unlikely to cause complications, and the oral drugs that are the most effective treatments can potentially cause hepatotoxicity and serious drug interactions. Some proposed indications for treatment include the following:

• Previous ipsilateral cellulitis

• Diabetes or other risk factors for cellulitis

• Presence of bothersome symptoms

• Psychosocial impact

• Desire for cosmetic improvement (controversial)

Treatment of onychomycosis is typically oral terbinafine or itraconazole. Terbinafine 250 mg once a day for 12 weeks (6 weeks for fingernail) or pulse therapy with 250 mg once a day for 1 week a month until the nail is clear achieves a cure rate of 75 to 80% and itraconazole 200 mg 2 times a day 1 week a month for 3 months achieves a cure rate of 40 to 50%, but the overall recurrence rate is estimated to be as high as 10 to 50%. It is not entirely necessary to treat until all abnormal nail is gone because these drugs remain bound to the nail plate and continue to be effective after oral administration has ceased; however, risk of recurrence may be higher in such cases. The affected nail will not revert to normal, but newly growing nail will appear normal. Fluconazole may also be an option.

The newer topical agents efinaconazole and tavaborole can penetrate the nail plate and are more effective than older topical agents.

Investigative treatments include new delivery systems for terbinafine. Topical antifungal nail lacquer containing efinaconazole 10%, ciclopirox 8%, or amorolfine 5% (not available in the US) is occasionally effective as primary treatment (cure rate of about 30%) and can improve cure rate when used as an adjunct with oral drugs, particularly in resistant infections.

To limit relapse, the patient should trim nails short, dry feet after bathing, wear absorbent socks, and use antifungal foot powder. Old shoes may harbor a high density of spores and, if possible, should not be worn.

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

1. Update on current approaches to diagnosis and treatment of onychomycosis (2018)