Osteopetrosis. Note the dramatically increased density throughout this patient’s bones. The patient has osteopetrosis, in this case the autosomal recessive form (patients with the autosomal dominant form tend not to survive to adulthood). Although the bones are extremely dense, they are actually brittle and these patients may present with recurrent fractures. Another potential complication is compression of cranial nerves as they exit the skull base, and narrowing of the medullary cavities resulting in replacement of the bone marrow, which may result in anaemia and neutropenia.