Muscle and Bone Flashcards
Duchenne Muscular Dystrophy
- X-linked disorder caused by mutations leading to non-functional dystrophin protein–responsible for translation of force between muscle and surrounding connective tissue.
- occurs almost entirely in male children
- weakness of proximal muscles, starting at age 1, then progressing to immobilization. death in early teens due to pneumonia from respiratory muscle weakness.
- histo–varying fiber size, necrosis of individual muscle fibers, replacement of dead fibers with fibrofatty tissue.
dystrophin gene is located on short arm of X chromosome
–will show compensatory hypertrophy of distal sites (calf) followed by pseudohypertrophy, due to increased fibrous/fatty tissue deposition.
Becker Muscular Dystrophy
similar to Duchennes, but much more rare and much less severe.
dystrophin is not totally absent, just a truncated or mishaped protein takes the normal ones place
sx onset later on in life, much less severe.
Dermatomyositis
- classically presents with lilac heliotrope rash with periorbital edema, along with dusky red patches (Grotton’s lesions) on extensor surfaces.
- Proximal muscle weakness occurs first, loss of fine motor control only occurs in advanced stages of dz.
- inflammatory infiltrates (b cells) predominantly seen in the small blood vessels in perimysial CT. Atrophic fibers seen adjacent to theses affected blood vessels.
- seen in children and in adults–children onset of sx also seen with GI upset and abdominal pain.
- pt will show elevated ESR, CK, and positive ANA. (anti- Jo-1 diagnostic of DM)
Rhabdomyosarcoma
- most common soft tissue sarcoma in children
- embryonal is the most common variant, generally occurring at the head and neck, and genitourinary tract (usually devoid of skeletal muscle)
- histo–rhabdomyoblast is the diagnostic cell–large cell with abundant pink cytoplasm and eccentric nucleus is sea of undifferentiated embryonal rhabdomyosarcoma cells
Osteoporosis
- decrease in bone mass
- exact mechanism unknown, either impaired synthesis of bone, or increased resorption of bone matrix protein.
- results in bone structures inadequate for weight bearing and pathological fractures. most common fractures in vertebrae, hip, femoral neck.
- serum calcium, phosphate and PTH are usually normal.
histo– thinned cortices and trabeculae, widened Haversian canals
- estrogen inhibits osteoclastogenesis, so postmenopausal women will see an increase in bone loss.
- increased expression of RANK and RANKL– leads to osteoblastic activity
Osteoarthritis
primary ( noninflammatory) degenerative joint disease characterized by progressive loss of the articular cartilage, followed by thickening of subchondral bone, osteophyte formation, and inflammation of the joint space.
- generalized increase in bone density at affected joints due to subchondral sclerosis and cyst formation from increased pressure on bone.
- Heberdon’s and Bouchard’s nodes seen at PIP and DIP
- fractured osteophytes can roll around in joints–(joint mice)
AKA “wear and tear” arthritis
Osteosarcoma
- most common primary bone tumor with two age peaks: before 20 years and the elderly(usually with some other pathology).
- histologically will see tumor cells making osteoid. cells will show mutation of rb and p53 genes
- lytic mass that will show codman’s triangle on xray after periosteal eruption==> will also cause pain. will most commonly be seen in the metaphyses of long bones (tib/fem)
- common metastasis sites to the lungs and other bones (very malignant)
Paget’s Disease
- associated with disorganized bone metabolism with alternating and overactivity of osteoblasts and osteoclasts. will show “mosaic” pattern to bone due to alternating blast/clast activity– predominance of woven “new” bone.
- marked serum alkalin phosphatase (marks Ob activity), normal Ca, and Phos.
- bones are thicker, but lack strength due to disorganization
- can lead to osteosarcoma
- start out with osteolytic stage, then mixed blast/clast activity, followed by sclerotic stage
- Leontiasis–cranium involved, leads to difficulty holding head up and increased head size.
Chondrosarcoma
malignant cartilaginous tumor, 2nd most common primary bone neoplasm.
- men 30-60 years old, characteristic sites include pelvis, spine or scapula, ribs, axial skeleton
- histo– disorganized mass of chondrocytes making hyaline or myxoid cartilage, with more than one cell pre lacuna. tumors are gelatinous and lobulated, filled with neoplastic chondrocytes
- generally grow slowly, with occasional mets to lung, bone.
- grading directly correlates with prognosis.
Ewing’s Sarcoma
“small blue cell” tumor, commonly found in the diaphysis of long bones, peak incidence in boys under age 15
- characterized by a t(11;22) translocation that leads to overproduction of some gene product. (same as PNET)
- small blue cells with scant cytoplasm, reactive bone formation will give an onion-skin appearance.
- common early mets to lung, other bones, but responds well to chemo/surgery/radiation.
Giant Cell Tumor
“osteoclastoma”
- proliferation of long spindle cells intermingled with large, multinucleated giant cells resembling osteoclasts. commonly found in the epiphysis of long bones (knee)
- peak incidence age 20-40, women>men
- benign, but locally aggressive tumor.
- bone changes present similar to those of hyperparathyroidism, so need serum calcium and PTH. (can be confused with brown tumor of bone from HPT)
Osteoid Osteoma
benign bone tumor of osteoblasts that produce osteoid.
- painful lesions usually found in teenagers or 20s. If lesion is larger than 2 cm, it is called an osteoblastoma.
- Obs secrete PGE2 at night, causing nocturnal pain, that is made better by aspirin.
Osteogenesis Imperfecta
- 4 types, type 2 fatal in utero/perinatal, type 1 will have normal outcome
- brittle bone disease, caused by improper type 1 collagen
- blue sclera, prone to fracture, hearing loss, dental abnormalities– propensity for fractures clinically mistaken for child abuse.
Osteopetrosis
“marble bone disease” problem with resorption/sclerosis
-radiographic–“Erlenmeyer Flask” disorder– bone is larger at the distal end, very hard but brittle, prone to fracture
Avascular Necrosis
most often caused by some type of ishemia, will lead to wedge-shaped infarct
-specifically problematic when area of is in articular surface beneath the ccartilage–> problems with weight bearing, cartilage breakdown.
