Abstract
Checking the fungal elements using potassium hydroxide （KOH） direct examination is essential for the diagnosis and observation of the disease course of tinea unguium. Dermoscopy is also useful for observation. Treatment is either oral or topical administration of antifungal drugs. In Japan, most of the tinea unguium cases are caused by Trichophyton rubrum and Trichophyton mentagrophytes. In Japan, along with the rapid increase in the number of elderly people, studies have shown that the prevalence of tinea unguium increases with age. As the forerunning country in the world, we can prescribe the topical drugs 10% efinaconazole and 5% luliconazole for tinea unguium. We can develop new strategies against tinea unguium, but this topical treatment has a risk of nail discoloration. Thus, correct diagnosis of tinea unguium by dermatologists is important, and KOH direct examination is essential for not only diagnosis but also observation during treatment.
