Depressed finger caps may be caused by nail fungal disease, nail dystrophy, trauma and so on. 1. Nail fungal disease: the main causative agent is dermatophytes, after infection, the reproduction and destruction of fungi lead to deformation of nails, which is manifested as sunken nail plate, loss of luster, brittle and easy to buckle up. 2. Nail malnutrition: it may be related to the lack of trace elements or stimulation of chemical agents, and it can also cause changes in nail morphology, resulting in the appearance of nail transverse grooves, punctate depression and so on. 3. Trauma: trauma can lead to deformation of the nail plate and inward depression, such as finger crushing and smashing, all of which can lead to depression of the nail plate. There are many other causes of finger cap depression, due to the different causes of the treatment method as well as the severity of different, it is recommended to seek timely medical treatment, so as not to worsen the condition.