Definition: Onychomycosis (nail fungus) is a lesion caused by dermatophytic yeasts and non-dermatophytic mycobacteria that invade the nail plate or even the nail bed. Among them, the lesions caused by dermatophytes are originally called nail fungus. I. Pathogenic bacteria 1. dermatophytes, yeasts and non-dermatophytic mycobacteria; 2. dermatophytes account for about 65% or more. Trichophyton rubrum accounts for the first place; 3, yeast accounts for about 10-30%, mainly Candida albicans. Zhu Caiyong, Department of Dermatology, 89th Hospital of the Chinese People’s Liberation Army; 4, non-dermatophytic fungi account for about 3 to 12%, there are short broom mold, Fusarium, branch top spores, Aspergillus, column top spores and Canadian nail mold, can cause nail fungal disease, yeast and non-dermatophytic fungi have a rising trend in recent years. Lipophilic yeast Malassezia has also been reported. Second, the pathogenesis and pathogenic factors 1, patients with tinea pedis are prone to secondary nail fungal disease, and there is a certain relationship with toenail trauma; 2, the isolation rate of yeast in the diseased nail and the environment of the wet temperature, the site of infection and the gender of the patient are closely related; 3, dermatophytes have pro-keratin; 4, the pathogenic mechanism of mold in nail fungal disease has yet to be further explored. 3, incidence 1, foreign literature reports the incidence of natural population is 2-18%, more than 70 years old for 50%; 2, the domestic natural population incidence of 15%, Hong Kong reported 17-21%; 3, nail fungal disease accounted for 30% of superficial fungal disease, accounting for 50% of nail disease, toenail incidence is four times the nail More than; 4, the incidence of diabetic patients is 26.2%, 2.77 times more than normal people. Clinical manifestations 1, superficial white spot type (SWO); 2, distal (lateral edge) sub nail type (DLSO); 3, proximal sub nail type (PSO); 4, intra nail plate type (EO); 5, total nail destruction type (TDO). If yeast and / or non-dermatophytic mycobacteria are cultured, repeat the culture for 2 times, or use a multi-point culture in a flat dish, six of the ten growth points are the same fungus and direct microscopy with the same positive findings can be judged as the pathogenic bacteria. 3, pathological examination. 6, diagnostic criteria 1, typical clinical manifestations; 2, positive fungal microscopy and/or positive fungal culture; 3, histopathological examination of the diseased nail found fungal components: (1) with 1, 2, 3 or 1, 2 or 2, 3 can be diagnosed as a fungal nail fungal disease. (2) If there are 1, 3 or 1 and positive microscopy, the diagnosis is nail fungal disease, but the causative organism is not identified. In addition, it should be distinguished from other nail diseases, such as psoriasis, eczema, lichen planus and nail dystrophy caused by nail changes. VII. Treatment 1. Systemic treatment; 2. Local treatment; 3. Removal of diseased nail; 4. Adherence to a combination of basic therapy and individualization. (1) Systemic therapy Itraconazole, terbinafine, fluconazole All the above drugs need to be taken when the liver function is normal. It is recommended to test the liver function before and/or during the treatment if necessary, and attention should also be paid to the problem of drug interactions. (2) Itraconazole 1, wide antibacterial spectrum, good patient compliance, high efficacy and safety features, whether dermatophytes or yeasts and/or non-dermatophytic mycobacteria caused by clinical types of nail fungal disease, can be used for the treatment of this drug. 2, impact therapy twice a day, each time 0.2, at mealtime or after meals that take, take 7 days, stop 21 days for a course of treatment, nail fungal disease 2 ~ 3 courses, toenail fungal disease 3 ~ 4 courses of treatment. 3.Continuous therapy 0.2 daily, 2-4 months of continuous medication. (3) terbinafine 1, terbinafine is also efficient and safe broad-spectrum antifungal drugs, especially for nail fungal disease caused by dermatophytes 2, usage: 0.25g per day, nail fungal disease 6-9 weeks, toenail fungal disease 9-12 weeks (4) fluconazole 1, the drug is widely used in candidiasis, so the nail fungal disease caused by Candida, can be treated with fluconazole 2, 0.15 ~ 0.3 per week g, tonics, nail fungal disease for 3-6 months, toenail fungus for 6-9 months. Adhere to the combination of basic therapy and individualization. VIII. The course of treatment should be extended appropriately in the following cases: 1, combined with nail fungus and nail matrix damage; 2, slow nail growth.