Malignant Infantile Osteopetrosis (autosomal recessive osteopetrosis) is a rare congenital disorder of bone resorption characterised by generalised skeletal densification. Thus OsteoPETROSIS may be considered as the opposite to OsteoPOROSIS, where bone density is decreased. Excessive bone density can interfere with vital tissues and structures, causing serious problems throughout the body. Compression of nerves in the skull, for example, can lead to problems such as vision loss and breathing problems. It can also cause crowding of the bone marrow, which is the tissue inside the bones that produces blood cells and platelets. The specific complications and their severity depend largely on the type of osteopetrosis. Most of the life threatening severe forms of osteopetrosis can be treated by allogeneic stem cell transplantation.