The absence of a crescent in the nail is generally normal, but certain diseases such as nail psoriasis, liver and kidney failure can also lead to changes in the crescent of the nail. 1. The size and number of crescents on the nails generally vary from person to person, and it is normal if there are no crescents. In addition, with age, there can be a gradual decrease in the number of crescents, which is a normal physiological phenomenon. 2. If the crescent suddenly becomes less and disappears within a short period of time, there may be nail psoriasis, which may lead to the disappearance of the crescent and brittle nails. In addition, if there are systemic diseases such as liver and kidney failure, the disappearance of the crescent may also occur. It is recommended that the patient exclude physiological factors, go to the hospital, clarify the cause of the disease, and promptly carry out the appropriate treatment of the original disease.