Chronic granulomatous disease develops when a specific gene from both parents passes to the child. This gene causes cells to develop abnormally in the immune system. The cells that are abnormal are called phagocytic cells. They normally kill bacteria. With this disease, these cells cannot work properly. As a result, the body can not fight some types of bacteria. It also makes infections likely to return.

CGD is a rare condition.

The disease is usually caused by a recessive gene. This means two of these defective genes have to be present for the disease to develop. This gene is carried on the X chromosome. Both parents must have the gene.