Flat toenails may be related to genetic factors, but also calcium deficiency, nail fungus and other factors. 1. Genetic factors: if there is a family with flat toenails, then the next generation may have such a situation, generally do not need special treatment, usually pay attention to the care of toenails. 2. Calcium deficiency: if the patient has flat toenails, and also accompanied by short stature, night terrors, excessive sweating and other aspects of the situation, may be due to calcium deficiency or lack of other nutrients. 3. ringworm of the nail: due to fungal infection, can lead to toenail nail plate deformation, discoloration, can also cause toenail become flat. The patient appeared to the toenail flat may have other reasons, it is recommended to go to the hospital in a timely manner for relevant examination, clear cause of the disease after active symptomatic treatment.