The appearance of vertical lines on the fingernails may be the result of other conditions such as onychomycosis, trauma, subungual melanoma, or onychomycotic nevus. 1. Tinea cruris: the etiology of tinea cruris is related to dermatophyte infection, or may be caused by tinea pedis, local blood circulation disorder, impaired immune function and other factors. Patients may have turbid nail plate, splitting, atrophy, shedding and other symptoms, which may be manifested as the appearance of vertical lines on finger nails. 2. Trauma: If the patient’s fingernail has been hit or squeezed recently, it may lead to local blood circulation disorder and the appearance of vertical lines on the fingernail. 3. Subnail melanoma: Subnail melanoma is a kind of malignant melanoma, which may be caused by heredity, trauma, inflammation and other factors. Symptoms are the gradual blackening of the nail plate after longitudinal cracking, and with the progress of the disease, blood-like secretion may appear, which is manifested as the appearance of vertical lines on the fingernails, and preferably occurs in the thumb (toe). 4. Others: vertical lines on fingernails are also considered to be caused by onychomycosis, malnutrition and other diseases. There are many reasons that lead to the appearance of vertical lines on the fingernails, it is recommended that patients go to the regular hospital for relevant examinations, so as to clarify the causes of the disease and standardize the treatment.