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13 Cards in this Set

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  • Back

bony dysplasias and similar problems affect what (compared to bone infections, tumors etc.)

affect ALL OR MOST of skeleton versus infections, tumors, etc, dysostoses (hard to separate, individual or groups of bones (morphogenic)); present young and old; cells and/or matrix components (innumerable); SELECTED FEW CAN MIMIC TUMORS (beware)

general features (the characteristics that are in all bony dysplasias)

similar clinical features in many diseases= pathological fractures, deafness, early osteoarthritis, highly variable extraosseous involvement

abnormality signaling: cartilage: achondroplasia

generalized (cartilage model bones); spontaneous mutation 80%; autosomal DOMINANT; point mutation= fibroblast growth factor receptor 3 (FGFR 3) (4p16.3), receptor constantly activated; short limb dwarfism with NORMAL intelligence; thanatophoric dwarfism= #1 lethal dwarfism at 1 to 20,000 (Lys650Glu)

abnormal collagen: extraskeletal: structural protein

bone type I collagen- osteogenesis imperfecta (OI)= defects in alpha1 or alpha2 chain, too little normal collagen or abnormal collagen, multiple types and counting, with rearrangements, some mild, some lethal in utero, abnormal collagen variants worse, affects extraosseous tissue also, but variably; cartilage= overall 1000 mutations in 22 genes collagens 2 and 9= matrix problems

osteogenesis imperfecta clinical features

FRAGILE BONES= PATHOLOGICAL FRACTURE; wormian skull= unfused bone islands in skull; extraosseous= blue sclera, inguinal hernias, joint laxity, hearing and teeth problems; severity range wide

so why remember OI?

incidence= 1 per 10,000 to 20,000 children; child abuse more common at 2-3 per 1,000 children; but may need to test to exclude OI in selected cases= test COL1A1 and COL1A2, sensitivity 90%, less common mutations hard to detect, VERY expensive ($3000-$4000) now

fibrous dysplasia

focal or multifocal lesions in cancellous (spongy) bone= developmental defect; poor bone formation without normal maturation of structure; 'ground glass' appearance on x-ray; irregular bone spicules WITHOUT osteoblast rimming; pathological fractures= shepard's crook deformity proximal femur from multiple fractures; 70% monostotic (axial, prox. ext., these may mimic tumors), 27% polyostotic (also distal ext.), 3% McCune (Albright's syndrome, somatic mutation excess CAMP- GNAS1 locus mosaicism of 21q, plus endocrinopathy)


albers schonberg or marble bone disease; mixed causes related to acidification of bone by osteoclasts to release mineral, rare; some recessive (worse) or dominant (better) inheritance patterns; DEFECT IN OSTEOCLAST FUNCTION= carbonic anhydrase 2 deficient, other identified defects; think UNREMODELED bone and persistent calcified cartilage spicules; BRITTLE= PATHOLOGICAL FRACTURES; worst= cranial nerve compression, infections (BM spaces limited)

paget disease of bone

long considered acquired disease, possibly viral, who knows; some studies show familial link (18q, 18q is a hotspot for LOH in sporadic as well as Paget osteosarcoma, SQSTM1 gene mutations enhance NK-kappaB activation); uncontrolled bone turnover driven by OSTEOCLASTS; normal calcium metabolism, very HIGH serum alkaline phosphatase (bone specific); monostotic or polyostotic; most axial skeleton or proximal femur; early= extensive osteoclastic resorption with highly vascular fibrous marrow; late= fragile MOSAIC lamellar bone

paget disease of bone: symptoms

enlarged coarse bones, all brittle; pathological fractures at all stages; deafness; high bowing and pain; secondary osteoarthritis; secondary sarcomas rare (<0.1%)- 50% osteosarcomas; treatment= symptomatic, bisphosphonates

osteomalacia and ricketts

inadequate mineralization of bone and calcifying cartilage; childhood ricketts; osteomalacia= unmineralized osteoid seams so normal or increased osteoid but too little mineral (x-ray osteopenia aka too little bone); variable serum Ca/Po4


cannibalization of skeleton to maintain serum calcium; results= osteoclastic resorption of bone, marrow fibrosis; serum calcium, phosphate depend on underlying disease; generalized osteopenia most common presentation now, localized disease less common

renal osteodystrophy

secondary hyperparathyroidism; osteomalacia; metabolic acidosis increases resorption; iron and aluminum deposition; amyloid; protein abnormalities with poor matrix; results mutlifactorial and variable