INTRODUCTION
Onychomycosis is the most common fungal infection
comprising about one-third of all skin fungal infections,
and 50% of all nail disorders.1,2 It is well recognized
in dermatology practice that onychomycosis and tinea
pedis can exist together in the same patient, that tinea pedis
can lead to onychomycosis, and that it is important to evaluate
and treat both diseases.3 Once the nails become infected, they
become reservoirs for continued infection of the surrounding
skin, potentially resulting in a cycle of re-infection.4 However,
data showing the impact of treating co-existing tinea pedis on
onychomycosis outcomes, and the potential to reduce onychomycosis
recurrence or re-infection is lacking.
Prevalence of Onychomycosis and Co-Existing Tinea Pedis
Onychomycosis has been found to be significantly more
likely to be diagnosed in the context of tinea pedis (P<.001),5
with a history of tinea pedis more than doubling the risk of
onychomycosis.6 Although the true prevalence of co-existing
onychomycosis and tinea pedis is unknown, a number of
surveys have suggested that about one third of patients with
toenail onychomycosis also have tinea pedis.7-9
In a large survey of over 2700 patients with toenail onychomycosis,
42.8% had concomitant fungal infections, with tinea
pedis being most common (seen in 33.8% of patients).7 Interdigital
tinea pedis was the most common subtype noted in
over 65.4% of cases.7
The extent of toenail onychomycosis and recurrent disease were
found to be the most important parameters influencing the coexistence
of tinea pedis.7 Their co-existence is more commonly
seen in men, and increases with age. Not surprising as both tinea
pedis and onychomyosis are more common in men; and it has
been estimated that 25.7% of elderly patients have both diseases,
10 where more advanced disease, greater non-target toenail involvement, and longer disease duration are all commonplace.7
A recent study in subjects with diabetic foot complications also
showed a high prevalence of both types of infection, with tinea
pedis observed in 46.7% and onychomycosis in 53.3% of subjects,
compared to a prevalence of 14.7% an 22.7% in matched
controls.11
Treatment of Onychomycosis and the Implications of Co-Existing Tinea Pedis
Left untreated, onychomycosis and tinea pedis have the potential
to cause further morbidity such as wounds, cellulitis, secondary
bacterial infection, pain, and difficulty with ambulation, particularly
for individuals with a compromised health status.12-14 In
addition, recurrence (relapse or re-infection) of onychomycosis is
not uncommon, with reported rates ranging from 10% to 53%.15-17
It is also worth mentioning that many patients with toenail onychomycosis
and/or tinea pedis are not aware that they have fungal
infection, and may not seek medical care and such patients pose a
special challenge for physicians to detect and treat the disease.18-20
For effective onychomycosis therapy it is essential not only to
treat the affected toenails but also to prevent spreading the
infection to other sites of the skin. Prevention of onychomycosis
includes adequate treatment of any concurrent tinea pedis,
and screening and treating family members for co-existing
disease.21 In addition, it has been suggested that an unnoticed
and stable reservoir of dermatophytes in the nail plate can
lead to infection and re-infection of the surrounding cutaneous
surfaces such that effective long term cure of tinea pedis
may require nail-directed therapy.5,6
Treatment of Onychomycosis and Co-Existing Tinea Pedis
Despite the clear need to look for and treat both diseases concurrently,
there are few clinical data in practice to support this
