The greatest number of bone tumors are benign, either simple cysts or proliferation of normal tissue, such as cartilage, bone, vascular or fibrous tissue, in bone. The most common malignant tumors found in bone are metastatic tumors spread from cancer in sites such as the breast or prostate. Malignant tumors that are not related to other cancers called sarcomas in connective tissue, made of bone, cartilage, or fibrous tissue, may occur in the bone. Components of the marrow may also produce sarcomas.
An infection of bone is called osteomyelitis. These infections are usually caused by bacteria such as Staphylococcus, Streptococcus, or colon bacteria. In children, osteomyelitis is often caused by bacteria from infections occurring in the tonsils or ear that spread via the blood stream. Before antibiotics were widely available to treat these infections, osteomyelitis was common and often caused serious illness and deformity; now, the illness does not occur as often. Osteomyelitis requires immediate treatment, because these infections develop rapidly in children. If the infection involves the joints, complete joint destruction may occur within 24 hours. Adult infections are more often associated with open fractures or surgery. In rare cases, tuberculosis, syphilis, fungi, viruses, and parasites cause bone infections.
Some diseases and defects of bone have a genetic cause. These include extra toes and fingers, missing, short, or strangely shaped bones. Other genetic diseases cause defects in the quality of the bone-forming cells. In osteogenesis imperfecta, the bone cells cannot form normal collagen; the bones are thin, short, and easily fractured. In osteopetrosis, bone cells called osteoclasts fail to resorb and remodel bone, resulting in weak, dense bones that have little marrow. People with osteopetrosis may have anemia.
There are many bone diseases and syndromes that are congenital, or present at birth. Congenital bone diseases constitute a wide spectrum, ranging from the less severe, such as mild flat feet, to severe lesions, such as spina bifida, in which the lower end of the spine fails to develop properly and the baby is born with paralysis and misshapen vertebrae. Congenital diseases may have hormonal bases. Disorders of growth include several kinds of dwarfism and gigantism.
Bones may develop deformity as the result of known causes, such as poliomyelitis, or unknown causes, or due to one of several causes, such as curvature of the spine (scoliosis) or clubfoot.
Other examples of congenital bone diseases are congenital hip dislocation, congenital torticollis (wry neck), Klippel-Feil syndrome (short webbed neck with two or more vertebrae fused), and Sprengel deformity (elevated scapula).
Two children's diseases deserve special mention. The first is slipped capital femoral epiphysis. This occurs in early adolescence and involves the head of the femur slipping off the growth plate. The second is Legg-Calve-Perthes disease and involves interruption of blood supply to the child's hip. This usually occurs in children 3 to 8 years of age. Either disease may result in a permanently damaged hip joint.
Bones are a rich storehouse of minerals such as calcium, magnesium, and phosphorus. Metabolic diseases of bones generally affect the bone's ability to process these minerals correctly. The most common metabolic diseases are osteoporosis, a disease that causes brittle bones, and rickets (in children) or osteomalacia (the adult form).
If the pituitary gland is hyperactive in adult life, acromegaly may result with increased bony prominence of the bone beneath the eyebrows and in the hands. Diseases of the kidney can cause a metabolic imbalance of phosphate and calcium so that bone weakening occurs. Other metabolic bone diseases include gout and Paget disease.
Bone disease may be caused by toxins. The most common toxinis lead, found in old paint or old plumbing. Lead paint eaten by children may be deposited in the bones as well as in other organs. Radium is another poison. Watch dials used to be painted with radium by hand, and the workers licked the tips of the brushes to keep a neat point; many eventually were stricken with anemia or bone tumors. Fluoride poisoning and radiation toxicity, as occurred at Hiroshima or Chernobyl, are other causes of bone disease.
Arthritis (inflammatory) or arthrosis (non-inflammatory) involves the ends of bone which join other bones. Examples of arthritis include _Lyme disease and rheumatoid arthritis. An example of arthrosis is osteoarthritis.