MSK Pathology Flashcards
Osteogenesis Imperfecta
AD defect in collagen type I synthesis
Clinical Features: multiple fractures of bone (can mimic child abuse); blue sclera (thinning of collagen reveals underlying choroidal veins); hearing loss (bones of middle ear easily fractured)
Osteopetrosis
Inherited defect of bone resorption resulting in abnormally thick, heavy bone that fractures easily; Due to poor osteoclast function;
Variants: carbonic anhydrase II mutation –> loss of acidic microenvironment required for bone resorption
Clinical Features:
1) bone fractures;
2) anemia, thrombocytopenia, leukopenia with extramedullary hematopoeisis due to bony replacement of marrow (myelopthisic process)
3) vision and hearing impairment due to impingement on cranial nerves
4) hydrocephalus due to narrowing of foramen magnum
5) renal tubular acidosis because of decreased tubular reabsorption of HCO3- –> metabolic acidosis
Achondroplasia
AD; Impaired cartilage proliferation in the growth plate due to an activating mutation in fibroblast growth factor receptor 3 (FGFR3) –> inhibits cartilage growth
Does not affect intramembranous bone formation only endochondral bone formation
Osteomalacia
Defect in mineralization of osteoid due to low levels of CIt D –> low serum calcium and phosphate
Lab findings: decreased serum Ca2+ & phosphate, increased PTH, increased Alk Phos due to activation of osteoblasts
Osteoporosis
Reduction in trabecular bone mass resulting in porous bone with increased fracture risk
Risk is based on peak bone mass at age 30 based on genetics, diet and exercise, and rate of loss that follows; Can accelerate bone loss with lack of weight bearing exercise, poor diet, glucocorticoids or decreased estrogen
Clinical Features: bone pain and fractures in weight bearing areas such as vertebrae, hip and distal radius; Serum calcium, phosphate, PTH and alk phos are normal
Paget Disease of Bone
Imbalance between osteoclasts and osteoblasts; Usu seen in people >60; May have a viral etiology (Paramyxoviridae viruses)
Three distinct phases:
1) Osteoclastic (excessive RANK signaling and NF-kB activation 2) mixed 3) osteoblastic/osteosclerotic –> thick, sclerotic bone that fractures easily
Biopsy reveals mosaic, hypovascular disorganized pattern of lamellar bone with cement lines
Clinical Features: bone pain due to microfractures, increased hat size, hearing loss, lion-facies, isolated elevated Alk Phos
Tx. Calcitonin and Bisphosphonates
Complications: high output cardiac failure due to AV shunts, osteosarcoma
Osteomyelitis
Infection of bone; Usu in children; usually at metaphysis of long bones
Causes include: staph aureus, gonorrhoeae, salmonella (sickle cell), pseudomonas (diabetics or IV drug abusers), pasteurella (cat or dog bites/scratches), m. tuberculosis (vertebrae)
Clinical features: bone pain with signs of systemic infection (fever and leukocytosis), lytic focus surrounded by sclerosis of bone on x ray (sequestrum surrounded by involucrum)
Osteoid Osteoma
Benign tumor of osteoblasts surrounded by rim of bone
Occurs in young adults; Arises in the cortex of long bones
Presents as bone pain that resolves with aspirin
Imaging reveals a bony mass (2cm) and arises in vertebrae and does not respond to aspirin
Osteochondroma
Benign tumor of bone with overlying cartilage cap; Arises from lateral projection of the growth plate (metaphysis); Bone is continuous with marrow space; Overlying cartilage can transform to chondrosarcoma
Osteosarcoma
Malignant proliferation of osteoblasts; Peak incidence in teenagers; Risk factors: familial retinoblastoma, Paget disease, radiation exposure
Arises in metaphysis of long bones usu. distal femur or proximal tibia
Presents as pathologic fracture of bone with pain and swelling
Imaging reveals a destructive mass with ‘sunburst’ (tiny fragments) appearance of lifting of the periosteum (Codman Triangle); Biopsy reveals pleomorphic cells that produce osteoid
Giant Cell Tumor
Tumor comprised of multinucleated giant cells and stromal cells; Occurs in young adults; Arises in the epiphysis of long bones usually in distal femur and proximal tibia
“Soap-bubble” appearance on X-ray
Ewing Sarcoma
Malignant proliferation of poorly-differentiated cells derived from neuroectoderm; Arises in diaphysis of long bone; Usu. M <15 yo;
Onion-skin appearance on X-ray
Biopsy reveals small, round blue cells that resemble lymphocytes (can be confused with lymphoma or chronic osteomyelitis); t11;22 translocation
Often presents with mets
Chondrosarcoma
Malignant cartilage forming tumor
Arises in medulla of the pelvis or central skeleton
Prostatic Cancer Mets
Osteoblastic lesions
Rhabdomyoma
Benign skeletal tumor
Cardiac rhabdomyoma associated with tuberous sclerosis
