Other Pathologic Conditions
other pathologic conditions of bones may be caused by infections, tumors, endocrine disturbances, or nutritional imbalances. Tuberculosis of bone and osteomyelitis (inflammation of the bone and bone marrow) are two infections sometimes seen in bone.
in humans, osteomyelitis usually is caused by staphylococci or streptococci that gain access to the bone by way of the bloodstream and develop into a general infection or by way of a wound, in which case the infection may remain local.Benign (slow-growing, noninvasive, and not likely to cause death) bone tumors are named according to the cells of bone from which they originate. A tumor of bone tissue itself is called an osteoma. Chondromas may develop from the epiphyseal cartilage or from unabsorbed islands of cartilage that preceded the developing bone. Tumors develop and grow as a result of intrinsic changes in the cells of origin, but bony growths may also occur on the surface of a bone simply in response to prolonged irritation. Such growths are called exostoses.
Malignant tumors grow rapidly, metastasize (spread to other locations), and are often fatal if not treated. Osteogenic sarcomas are malignant tumors of bone that most commonly develop near the ends of long bones. Sarcoma is a general term for malignant tumors originating from tissues of mesodermal origin, such as connective tissue.
Osteodystrophy is a general term for any abnormality in bone development. Many osteodystrophies are due to some abnormality in the normal regulation of calcium and phosphorus. The abnormality could be produced as a result of an inappropriate diet or some disease state disrupting calcium and phosphorus regulation.
Rickets in young, growing animals and osteomalacia in adults are conditions of inadequate mineralization of osteoid. without appropriate mineralization, bones are relatively weak and flexible. Both rickets and osteomalacia usually are due to a lack of vitamin D, which is required for normal absorption of calcium from the gastrointestinal tract. However, they may also be caused by an imbalance or lack of calcium and/or phosphorus in the diet. Rickets chiefly affects the growing areas in bone, while osteomalacia, sometimes called adult rickets, affects the entire bone, since there are no rapidly growing areas in adult bone.
Achondroplasia is a hereditary condition in which the metaphyses fuse early in life, but the bones continue to increase in diameter. An animal affected with it is called an achondroplastic dwarf. The dachshund is a breed of dogs selectively bred for this condition. Dwarfism in cattle closely resembles achondroplasia.