There are more reasons for the deformation of toenails, and the common causes include nail fungal disease, psoriasis, trauma and so on. 1. Nail fungal disease: this disease is mainly caused by dermatophyte infection, followed by yeast and molds, mostly directly infected by tinea pedis, susceptible factors such as diabetes, immune deficiency, etc., manifested as thickening and discoloration of the whole nail, or the whole nail mutilation, surface inequality and other symptoms. 2. Psoriasis: the cause of this disease is not clear, may be related to cellular immune response, genetic factors, environmental factors, etc., after violating the nails, there will be nail deformation, roughness, depression and other symptoms. 3. Trauma:If the nails are traumatized, the effect of trauma will lead to bruising under the nails, nail deformation, depression and so on. It is recommended that patients combine their own situation, if necessary, to the regular hospital dermatology department, follow the doctor’s instructions to clarify the diagnosis and active treatment.