Vertical stripes appear on nails, which may be a lack of vitamin A or indicate chronic inflammation in some tissues and organs of the body. If there are vertical lines on the fingernails at the same time, it may be a sign of liver disease. If only one nail appears, it may be caused by trauma. If the longitudinal ridge is obvious, it can be seen in peripheral circulation disorder, flat moss and follicular keratosis, and the longitudinal ridge is beaded, which is the characteristic of rheumatoid arthritis.