Osteopetrosis

Osteopetrosis, literally "stone bone", also known as marble bone disease or Albers-Schönberg disease, is an extremely rare inherited disorder whereby the bones harden, becoming denser, in contrast to more prevalent conditions like osteoporosis, in which the bones become less dense and more brittle, or osteomalacia, in which the bones soften. Osteopetrosis can cause bones to dissolve and break. It is one of the hereditary causes of osteosclerosis. It is considered to be the prototype of osteosclerosing dysplasias. The cause of the disease is understood to be malfunctioning osteoclasts and their inability to resorb bone. Although human osteopetrosis is a heterogeneous disorder encompassing different molecular lesions and a range of clinical features, all forms share a single pathogenic nexus in the osteoclast. The exact molecular defects or location of the mutations taking place are unknown. Osteopetrosis was first described in 1903, by German radiologist Albers-Schönberg. Despite this excess bone formation, people with osteopetrosis tend to have bones that are more brittle than normal. Mild osteopetrosis may cause no symptoms, and present no problems. However, serious forms can result in the following: Stunted growth, deformity, and increased likelihood of fractures Patients experience anemia, recurrent infections, and hepatosplenomegaly due to bone expansion leading to bone marrow narrowing and extramedullary hematopoiesis It can also result in blindness, facial paralysis, and deafness, due to the increased pressure put on the nerves by the extra bone Abnormal cortical bone morphology Abnormal form of the vertebral bodies Abnormality of temperature regulation Abnormality of the ribs Abnormality of vertebral epiphysis morphology Bone pain Cranial nerve paralysis Craniosynostosis Hearing impairment Hypocalcemia Malignant infantile osteopetrosis Autosomal recessive osteopetrosis (ARO), also known as malignant infantile osteopetrosis or infantile malignant osteopetrosis (IMO), is a rare type of skeletal dysplasia characterized by a distinct radiographic pattern of overall increased density of the bones with fundamental involvement of the medullary portion.