Term
| what characterizes osteogenesis imperfecta? |
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Definition
| osteogenesis imperfecta/brittle bone disease is a relatively uncommon condition due to abnormal development of type 1 collagen. pts present w/multiple bone fractures, blue sclera, hearing loss, dentinogenesis imperfecta, scoliosis, and short stature. |
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Term
| what are the different types of osteogenesis imperfecta? |
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Definition
| type I: incompatible w/life. type II: perinatally lethal. type III: progressive and deforming, but survivable. type IV: survivable. |
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Term
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Definition
| osteopetrosis aka marble bone/albers-shonberg disease is a rare bone disorder involving reduced bone resorption and diffuse symmetric skeletal sclerosis due to impaired formation/function of osteoclasts. the bones take on a stone-like quality, but are brittle and can fracture easily. it is due to mutations which interfere w/the process of acidification of osteoclast resorption pit needed to dissolve calcium hydroxyapatite in the matrix. |
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Term
| how does osteopetrosis affect the skeleton? |
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Definition
| the bones lack a medullary canal and the ends of long bones are bulbous (erlenmyer flask deformity). the neural foramina are small and compress exiting nerves. primary spongiosa fills the medullary cavity, interfering w/ hematopoietic bone marrow and preventing formation of mature trabeculae. deposited bone is not remodeled and is woven into the architecture = increased fragility. depending on the type of osteopetrosis, the number of osteoclasts may be increased/decreased/normal. |
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Term
| what is severe infantile malignant osteopetrosis? |
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Definition
| this is characterized by fracture, anemia, and hydrocephaly and may result in postpartum mortality. if the child survives, they are likely to develop cranial nerve defects and severe infections (inadequate bone marrow). hepatosplenomegaly occurs due to extramedullary hematopoiesis. milder forms may not be detected until adolescence/young adulthood. |
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Term
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Definition
| a decrease in bone mass = increased bone fragility due to structural changes (loss of horizontal trabeculae and thickened vertical trabeculae) |
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Term
| what are the genetic associations w/osteoporosis? |
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Definition
| RANKL, OPG, and RANK which all encode key regulators of osteoclasts may be mutated as well as the MHC locus and/or estrogen receptor gene. |
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Term
| why does risk of osteoporosis increase w/age? |
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Definition
| osteoblasts in the elderly have reduced proliferative and biosynthetic potential |
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Term
| what mechanical factors may cause osteoporosis? |
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Definition
| decreased wt bearing exercise = increased bone weakness |
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Term
| what dietary factors can lead to osteoporosis? |
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Definition
| decreased Ca2+ in adolescent girls |
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Term
| what hormonal influences can lead to osteoporosis? |
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Definition
| estrogen deficiency post-menopausally stimulates cytokines which increase osteoclast activity via increasing RANKL levels and decreasing OPG levels. |
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Term
| what is osteomalacia/rickets? |
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Definition
| this occurs usually in children in developing countries w/open epiphyseal plates and a vit D deficiency. the vit D deficiency leads to decreased serum Ca2+ and phosphate which then causes accumulation of unmineralized bone due to defective mineralization. on x-ray, this appears as a cup-shaped deformity. |
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Term
| what are the 3 phases of paget's disease of the bone? |
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Definition
| 1) osteolytic phase: predominately osteoclasts replace marrow w/connective tissue. 2) mixed phase: osteclasts/blasts work together in bone resorption/formation. 3) osteosclerotic phase: irregular bone deposition causes a mosaic pattern (functionally unstable bone deposition). this usually affects the lumbosacral spine, pelvis, femur and skull. these pts may develop secondary osteosarcomas or fibrosarcomas. |
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Term
| what are the demographics of paget's disease of bone? |
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Definition
| most pts are > 55 y/o and live in n america, england, and australia. |
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Term
| what is the etiology of paget's disease of bone? |
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Definition
| mutations in SQSTM1 gene are present in 40-50% of patients, which enhances activation of RANK signaling leading to stimulated osteoclast activity and increased susceptibility to disease. etiology is uncertain, but has genetic and environmental connections. |
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Term
| what is the clinical presentation of paget's disease of the bone? |
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Definition
| usually asymptomatic at least initially. serum alkaline phosphatase is often elevated from osteoclastic activity. hypervascular bone lesions may be seen along w/warm skin and increased cardiac output. the head may be enlarged due to increased bone deposition along w/headaches, visual disturbances and deafness. transverse fractures of the long bones may also occur. |
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Term
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Definition
| infection of the bone, often due to staph aureus, e. coli, klebsiella, or proteus. salmonella is seen in sickle cell pts, h. influenza in newborns, and pseudomonas in IVDAs. these infections are very difficult to eradicate w/antibx. it is due to direct extension from joint/tissue hematogenously. traumatic implantation from sx or trauma can also cause this. |
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Term
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Definition
| TB infection of the spine (usually) |
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Term
| what characterizes acute osteomyelitis? |
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Definition
| neutrophilic infiltration, necrosis, subperiosteal abscesses, disruption of blood supply, and spread to/from joint capsule |
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Term
| what characterizes chronic osteomyelitis? |
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Definition
| sequela of acute infection, sequestrum (residual necrotic bone), involucrum (rim of reactive bone - like granuloma), brodie's abscess (abscess surrounded by sclerotic bone due to lack of good blood supply), and bacteria in sequestered areas. |
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Term
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Definition
| benign exophytic tumors of mature bone usually appearing in males 40-50 y/o. if on the flat bones of the skull, they may protrude into the sinuses. osteomas are associated w/gardner's syndrome. |
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Term
| what are osteoid osteomas? |
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Definition
| *painful* (pumps out prostaglandins) benign lesions on the femur/tibia (metaphysis) commonly occurring in males 10-30 y/o. on x-ray: central radiolucent nidus. |
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Term
| what is an osteoblastoma? |
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Definition
| similar to osteoid osteoma, osteoblastomas have a larger central nidus on x-ray and are found in the spine or large bones of the leg. theses are often painless and may be difficult to distinguish from osteosarcomas (if more cellular). |
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Term
| what is an osteosarcoma? who does it affect? where? |
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Definition
| the most common primary bone malignancy (beyond hematopoietic lesions like leukemia and plasma cell myeloma). they usually affect males to females in a 3:2 ratio at 10-25 y/o then after 40. usually osteosarcomas are found in the lower femur and upper tibia. |
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Term
| what is the pathogenesis of osteosarcomas? |
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Definition
| malignant cells form osteoids which extend from the marrow to cortex to soft tissue to epiphysis to the joint. codman's triangle is when the periosteum is lifted up as the osteosarcoma spreads to the cortex. there may be satellite nodules around the main tumor mass. this may destroy the preexisting bone or grow around it. usually metastasis occurs via blood to the lungs or other bones. regional lymph nodes are generally unaffected. |
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Term
| what are predisposing conditions for osteosarcoma? |
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Definition
| paget's disease (particularly in elderly pts), radiation exposure, chemotherapy, and trauma (doesn't cause - but may bring more prominent clinical signs) |
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Term
| what is an osteochondroma/exostosis? |
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Definition
| a benign tumor of cartilage and bone commonly occurring in males ~10 y/o in the metaphysis of the lower femur, upper tibia, and humerus. they grow opposite joint direction w/a mushroom-like cartilaginous cap. they are generally asymptomatic beyond potential mass effects and if single malignant transformation is rare. if multiple, there is a potential association w/gardner's syndrome. |
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Term
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Definition
| a common benign tumor of cartilage usually in the small bones of the hands, feet, and phalanges. chondromas are composed of hyaline cartilage w/focal areas of calcification and appear as popcorn-like densities on x-ray. |
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Term
| what syndromes are associated w/chondroma formation? |
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Definition
| olliers disease: unilateral chondromas+ovarian tumors. maffucci's syndrome: chondromas+soft tissue hemangiomas. the more chondromas = the higher the malignant transformation risk. |
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Term
| what is a chondroblastoma? |
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Definition
| painful cellular tumors which are locally aggressive but rare. they mainly affect males 10-20 y/o in the distal femur and proximal humerus and consist of immature cartilage which looks like *chicken wire. |
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Term
| what is a chondromyxoid fibroma? |
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Definition
| chondro: cartilage, myxoid: myxomatous background, fibroma: fibrous elements in a benign tumor. these appear in the long bones of young adults and appear as well defined lytic lesions on x-ray. if particularly cellular, they can resemble a low grade chondrosarcoma. they may recur if incompletely removed. |
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Term
| how does an chondrosarcoma present? prognosis? |
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Definition
| chondrosarcomas occur in the pelvis/ribs/shoulders of pts 30-60 y/o and in the extremities of children. they appear as osteolytic lesions w/areas of calcification on x-ray and permeate bone marrow. 2+ nuclei per cell is seen w/this as opposed to 1 per cell in chondromas. prognosis is better than that in osteosarcomas however metastasis may occur to the lungs. recurrence may also occur up to 20+ years later. |
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Term
| what characterizes incidence of giant cell tumors? |
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Definition
| typically giant cell tumors affect *younger asian women, mostly at the metaphyseal-epiphyseal junction of the lower femur, upper tibia, and lower radius, on x-ray: *lytic w/o sclerosis. histologically: giant cells in spindled stromal cells. all are potentially malignant, usually they met to the lung and radiation therapy may induce malignant transformation. |
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Term
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Definition
| this is a common primary bone malignancy in children, affecting the long bones, pelvis, ribs, and vertebra and is due to a t(11;22) translocation. ewing's sarcoma arises in the medullary cavity and may involve the entire bone (pain+increased fracture risk). on x-ray: distinct *onion skin layering of new bone. grossly: white+fleshy. histologically: sheets of small uniform cells ("small blue cell tumor") separated by strands of fibrous stroma. this may metastasize to the lungs, other bones, CNS, and lymph nodes. |
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Term
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Definition
| a gelatinous, soft, hemorrhagic (abundant mucoid matrix) tumor w/cells growing in cords+lobules separated by mucoid matrix. chordomas affect middle age males more often and are malignant - may destroy bone and/or met to skin and other bone. in adults this is usually found in the *vertebral bodies, *discs, and *sacrum. in children this is more likely to be seen in the *spheno-occipital area. *physaliferous cells* are specific to chordomas, which have large tumor cells w/bubbly cytoplasm. |
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Term
| what is fibrous dysplasia? what are the 3 kinds? |
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Definition
| an uncommon benign tumor-like lesion of the bone. 1) the monostotic type is most common and is seen affecting the ribs, tibia, and femur of teenagers. 2) the polystotic type is commonly seen in the face, pelvis, and femur and is associated w/endocrine abnormalities such as precocious puberty/hirsutism. 3) mccune-albright syndrome: unilateral bone lesions associated w/cafe au lait spots on the skin and endocrine problems such as precocious puberty. these appear well-circumscribed+radiolucent on x-ray and are often asymptomatic. histologically, proliferation of fibroblasts+collagen w/islands of woven bone is seen. |
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Term
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Definition
| this poorly defined lytic lesion is seen in the tibia, femur, ulna, and fibula (counterpart in jaw: ameloblastoma). histologically, *sclerosis is seen outlining lucent cells* and *spindle cells surround basaloid cells*. this is a low grade malignancy w/local recurrences, but rare lymph node mets. |
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Term
| what is the most common primary tumor of the bone/skull/spine/ribs? |
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Definition
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Term
| how does a malignant lymphoma appear? |
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Definition
| patchy w/cortical and medullary involvement. most are large cell type. |
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Term
| where are hemangiomas common? |
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Definition
| in the skull, vertebrae and jaw |
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Term
| what is the most common of all malignant bone tumors? |
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Definition
| metastases usually from the breast, lung, and prostate. most are osteolytic, but prostate/breast are osteoblastic. most are painful. 70% are seen in axial skeleton/30% in extremities. |
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Term
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Definition
| enlargement and disorganization of the chondrocytes leading to splitting of the articular surface, erosion of articular cartilage, and eburnation of underlying bone. osteophytes, bone excrescences may be seen on bone margins as a result. |
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Term
| how does osteoarthritis present clinically? |
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Definition
| wt-bearing areas such as the hips, knees, and lumbar/cervical vertebrae are affected. the PIP/DIP and first MCP/MTP joints are also affected. pain involved is described as deep+aching. |
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