Nail fungal disease refers to nail infections caused by any fungus, while onychomycosis refers specifically to nail infections caused by dermatophytes. nail fungal disease has an incidence of about 15% to 20% in people aged 40 to 60 years, and about 18% to 40% of nail disorders are caused by fungal infections. 30% of patients with dermatophyte infections and 50% of patients with tinea capitis have nail fungal disease and more women than men visit the clinic. As age increases, the number of patients increases. 1. Etiology and clinical manifestations Healthy nails are less susceptible to infection. The tendency of nail infection with fungi may be related to genetics, diabetes and local arterial circulation and lymphatic flow disorders, and peripheral neurological diseases. Toenails that work in humid environments and are frequently traumatized are susceptible to fungal infections. Toenail fungal disease is mostly transmitted directly from tinea pedis, while nail fungal disease may be transmitted from tinea cruris or infected by frequent foot scratches, and nail fungal disease is more common in toes than fingers. The pathogens of nail fungal disease include dermatophytes, yeasts, and molds. The most common dermatophytes are Trichophyton rubrum, Trichophyton spp. and Trichophyton floccosum. The same nail can be infected with two ringworm fungi, two dermatophytes plus a yeast (including Malassezia), or dermatophytes plus yeast and mold. Nail fungal disease can be clinically divided into four types, representing the site and degree of fungal invasion of the nail: ① white superficial type: limited punctate or irregular cloudy small pieces of damage; ② distal lateral subxiphoid type: the fungus initially invades the distal lateral edge of the nail; ③ proximal subxiphoid type: the infection begins in the nail epidermis sheath, and develops along the proximal nail root below and the nail epithelium; ④ total nail dystrophy type: is the ultimate end of the development of various nail fungal disease. The fungus invades the whole nail plate, the nail structure is completely lost, the nail matrix and nail bed are papilloma-like changes, covered with irregular keratinized material. The course of the disease is slow, and if left untreated, it is lifelong. It can sometimes be followed by nail fungus, causing localized redness, swelling, pus and pain. It seriously hinders fine finger movements. The appearance of the diseased nail also affects the patient’s social and self-confidence, reducing the quality of life. 2.Diagnosis and Differential Diagnosis Toenail deformation and discoloration, nail chip microscopy fungal positive, repeated culture for the same or several fungal growth, nail pathology or lysis nail smear fungal detection can confirm the diagnosis, sometimes need to be differentiated from psoriasis and flat moss, eczema or baldness caused by nail disease. 3, treatment for superficial, light, single nail fungal disease, can be used topical antifungal drugs. Severe nail fungal disease often requires internal antifungal drugs.