Chapter 18 - Musculoskeletal Flashcards
Cause of Achondroplasia?
Activating mutation in fibroblast growth factor receptor 3 (AD)
Why are sclera blue in osteogenesis imperfecta?
Because thinning scleral collagen reveals underlying choroidal veins.
Common cause of Osteopetrosis?
Mutation in Carbonic Anhydrase II that leads to the loss of the acidic microenvironment required for bone resorption.
Common clinical feature of Osteopetrosis?
Renal Tubular Acidosis due to decreased reabsorption of bicarb in tubules… Metabolic acidosis.
How to treat Osteopetrosis?
Bone marrow transplant (as osteoclasts are derived from MONOCYTES).
Rachitic rosary
Common finding in rickets. Due to osteoid deposition at the costochondral junction.
Laboratory findings with Osteomalacia? (calcium, phosphate, PTH, and alkaline phosphatase)
Low serum calcium and phosphate. High serum PTH and alkaline phosphatase.
Laboratory findings with Osteoporosis? (calcium, phosphate, PTH, and alkaline phosphatase).
ALL NORMAL.
Is Paget’s disease of bone diffuse or local?
LOCAL.
Biopsy findings in Paget’s Disease?
Mosaic pattern of lamellar bone. Thick, sclerotic bone that fractures easily.
What is the most common cause of isolated elevated Alkaline Phosphatase?
Paget’s disease of bone.
Two major complications of Paget’s disease of bone?
- High-output Cardiac Failure (due to formation of AV shunts in remodeled bone)
- Osteosarcoma
Where do osteomyelitis commonly seed in children vs. adults?
Children (transient bacteremia) - seed metaphysis.
Adults (open-wound bacteremia) - seed epiphysis.
Most common bacterial cause of osteomyelitis?
Staph aureus (but Salmonella in Sickle Cell Disease and Pseudomonas in diabetics/drug users)
Where do osteoma’s most commonly arise and what are the associated with?
Most commonly arise on the surface of facial bones.
Associated with Gardner syndrome (familial adenomatous polyposis and osteomas).
Common presentation of Osteoid Osteoma?
Bone pain that resolves with aspirin.
Common presentation of osteoblastoma?
Larger than osteoid osteoma, arises in vertebrae, and present as bone pain that does not resolve with aspirin.
What can osteochondroma progress onto?
Chrondrosarcoma
Risk factors to develop Osteosarcoma?
Familial retinoblastoma, Paget disease, and radiation exposure.
Where in the bone does osteosarcoma arise and what cell type is it made of?
Arises in the metaphysis of long bones, malignant proliferation of osteoblasts.
“Codman triangle” and destructive mass with sunburst appearance and lifting of the periosteum seen with?
Osteosarcoma.
Where do giant cell tumors arise, in what population, and what type of cell? Characteristic imaging?
Arise in the epiphysis of young adults, made of multinucleated giant cells. Present as “soap bubble appearance” on x-ray.
What type of cells produce Ewing Sarcoma?
Neuroectoderm!
What translocation is characteristic of Ewing Sarcoma?
t(11;22).
Where do chondroma’s arise?
Medulla of the small bones of the hands and feet.
Where do chondrosarcoma’s arise?
Medulla of pelvis or central skeleton.
What type of lesions are classically seen with metastatic bone cancer and what is the major exception?
Classically see lytic lesions. Exception is with prostate cancer, see sclerotic (osteoblastic) lesions.
What type of collagen makes up the articular surface of joints?
Type II (hyaline)
Heberden nodes are located where?
DIP
Bouchard nodes are located where?
PIP
RA is associated with which HLA type?
HLA-DR4
Hallmark lesion of RA?
Pannus formation (inflamed granulation tissue)
What is Rheumatoid Factor?
Fc portion of IgG (see IgM autoantibody against it)
What is found on fluid aspirate of RA joints?
Neutrophils and high protein.
What HLA group is associated with Seronegative Spondyloarthropathies?
HLA-B27
Three signs of Ankylosing Spondyloarthritis?
Arthritis of vertebrae, uveitis, and aortitis (aortic regurg common)
Thriad of Reactive Arthritis (Reiter’s)
Arthritis, Urethritis, and Conjuctivitis!
When do you see “sausage” fingers (arthritis of DIP joints most commonly)
Psoriatic arthritis.
What type of inflammatory cell do you see in the joints affected by gout?
Neutrophils!
Type of crystals in gout?
Monosodium urate crystals that are needle-shaped with negative birefringence under polarized light.
Type of crystals in pseudogout?
Calcium pyrophosphate dihydrate (CPPD) crystals that are rhomboid-shaped with weakly positive birefringence under polarized light…
What to screen for when having diagnosed dermatomyositis?
CARCINOMA (eg. gastric carcinoma)
What type of muscle weakness occurs in dermatomyositis?
Bilateral PROXIMAL muscle weakness. Distal can develop later.
Clinical and lab findings with dermatomyositis?
Heliotrope rash/malar rash with red papules on the elbows, knuckles, and knees (Grotton’s papules).
See ANA and Anti-Jo-1, with perimysial inflammation (CD4+) and perifascicular atrophy.
Lab findings with polymyositis?
Endomysial inflammation (CD8+) with necrotic muscle fibers.
What is X-Linked Muscular Dystrophy?
Mutation in DYSTROPHIN gene resulting in muscle wasting and replacement by adipose tissue.
Classic finding in Myasthenia Gravis?
Eye involvement –> ptosis and diplopia
Associated symptoms with Myasthenia Gravis?
Thymic hyperplasia or Thymoma… Thymectomy improves symptoms!
Most common cause of Lambert-Easton Syndrome?
Small cell carcinoma of the lung, producing anitbodies against presynaptic calcium channels. EYES USUALLY SPARED.
Most common benign soft tissue tumor in adults?
Lipoma!
Most common malignant soft tissue tumor in adults?
Liposarcoma! (made of LIPOBLASTS).
What is Cardiac Rhabdomyoma associated with?
Tuberous Sclerosis!
Most common malignant soft tissue tumor in children? Where are they found?
Rhabdomyosarcoma. Often located in the vagina of young girls.
What can you stain rhabdomyosarcomas with?
DESMIN!!!
