The main reasons for the bulging bones at the back of the head in infants include the following conditions. First, it is a symptom caused by vitamin D deficiency rickets in children. After vitamin D deficiency rickets occurs in infants, it causes softening of the skull, which can easily cause square skull and bulging bones at the back of the head. Children often have symptoms such as occipital baldness, corpus cavernosum, restless sleep at night, and excessive sweating, and the diagnosis can be confirmed by timely measurement of bone density, vitamin D and calcium levels in the blood. Secondly, if the child’s father or mother has a head shape with a bulging bone at the back of the head, the child will also have a bulging bone at the back of the head under the influence of genetic factors, and the growth and mental state are normal at this time.