The thumb nail bulge is mainly considered to be related to pathological factors such as vitamin deficiency, trauma, nail infection and psoriasis nail. 1. Vitamin deficiency: If the body lacks vitamin A and B, it can cause nail malnutrition, which can cause thumbnail bulging, in addition to the nail may be prone to become brittle, the symptom of being folded. 2. Trauma: If the thumb is extruded by external force, it may cause thumbnail bulge, if there is no obvious discomfort, proper trimming, usually can be slowly recovered. 3. Nail infection: If the thumb is infected with virus, bacteria, fungus, etc., especially fungal infection can cause onychomycosis, resulting in thumb nail bulging, thickening and darkening symptoms. 4. Psoriasis: the accumulation of keratin in psoriasis patients can cause nail hypertrophy, also known as psoriasis nail, thumb nail can be manifested as a raised symptom. Thumbnail bulging is not limited to the above diseases, so it is recommended to go to the hospital in time to find out the cause of thumbnail bulging, and actively treat it after a clear diagnosis, so as to avoid delaying the condition.