Osteopetrosis refers to a group of rare, inherited skeletal disorders characterized by increased bone density and abnormal bone growth. Symptoms and severity can vary greatly, ranging from neonatal onset with serious complications (such as bone marrow failure) to the incidental finding of osteopetrosis on X-ray. Depending on severity and age of onset, features may include fractures, short stature, compressive neuropathies (pressure on the nerves), hypocalcemia with attendant tetanic seizures, and pancytopenia. In rare cases, there may be neurological impairment or involvement of other body systems. Osteopetrosis may be caused by genetic changes in at least 10 genes. Inheritance can be autosomal recessive, autosomal dominant, or X-linked recessive with the most severe forms being autosomal recessive.