Onychomycosis refers to a fungal infection that affects the toenails or the fingernails. It is far more likely to involve the toenails and can involve all of the components of the nail unit, including nail matrix, nail bed and nail plate.

Since slightly more than half of all nail dystrophics are caused by fungus, diagnosis via KOH, DTM culture or tissue biopsy allows for differentiation from lichen planus, psoriasis, yellow nail syndrome and thyroid disease.

The incidence of onychomycosis in the U.S. has been reported to be up to 14% of the population, but may actually be much higher. It occurs most commonly in adults, most common after 60 years of age.

Successful treatment of onychomycosis involves thorough trimming and debridement of the infected nail tissue and the use of topical antifungal medications. Oral medications are commonly indicated when the fungus involvement is extensive. The published "iron-clad" study showed a significant increase in "clinical cure" when nail debridement was performed during the course of oral Lamisil administration vs. oral Lamisil use with no debridement.