Metabolic bone disease Flashcards
osteopenia and osteoporosis
10 million americans have full osteoporosis 34 million have osteopenia
Prognosis: prior fragility strongest predictor of future fracture
Vertebral fracture: 15% increase in 5 year mortality, increased morbidity
hip fractures: association with 20% increase in mortality
Increased morbidity: only 1/3rd of pts return to previous level function
Screening for osteoporosis and osteopenia
Treatments
dexa scan
Postmenopausal women and men over 50, hip/vertebral fracture
T score between -1 and -2.5 at femoral neck and spine
10 yr risk of hip fracture: greater than 3% or 10 yer risk of major osteoporosis-related fracture> 20%
Treatments: calcium and vitamin D
Bisphosphanates (IV can make jaw osteonecrotic, and atypical femoral fracture rarely), Conjugated estrogen progestin homrmone replacement therapy, estrogen only replacement, salmon calcitonin, raloxifene, teriparatide
Renal osteodystrophy
a pectrum of disease seen in patients with chronic renal disease, characterized by bone mineralization deficiency due to electrolyte and endocrine anormalities
Common cause of hypocalcemia (due to inabiity of the kidney to convert vitamin D3 to calcitriol) phosphate retention (hyperphosphatemia)
Hyperparathyroidism and secondary hyperphosphatemia Caused by hypocalcemia and lack of phosphate excretion
Uremia related phosphate retention
Associated conditions of renal osteodystrophy
osteomalacia (Adults) and growth retardation
avascular necrosis
tendonitis and tendon ruptures
Carpal tunnel syndrome
Pathologic fracture (brown tumor- hyper parathyroid)
Osteomyelitis
Symptoms of renal osteodystrophy
weakness, bone pain, skeletal deformity, symptoms of hypocalcemia (abdominal pain, muscle cramps, dyspnea, convulsions/seizures, mental status changes)
Imaging : loosers zones (white opacifications on neck of femur), brown tumor Large black hollow on head of fibula, rugger jersey spine (whisping on spines of vertebrae), varus deformity of femur in children (rounded), soft tissue calcification
LAB: ca is low, phos high, alk phos is high, pth is high
Treatment: treat the messed up renal condition
Rickets
a defect in mineralization of osteoid matrix caused by inadequate calcium and phosphate
Prior to closure if physis known as rickets
After closure of physeal called osteomalacia
Pathophys: disruption of calcium/phosphate homeostasis, poor calcification of cartilage matrix of growing long bones, occurs at zone of provisional calcification, leads to increased pyseal width and cortical thinning and bowing, Vit D and PTH play an important role in Ca homeostasis
Associated conditions of rickets
brittle bone with physeal cupping/widening, bowing of long bones, ligamentous laxity, flattening of skull, enlargement of costal cartilage (rachitic rosary), kyphosis
Familial hypophosphatemic rickets
VITAMIN D RESISTANT rickets, X linked hypophosphatemic rickets
Most common form of inheritable rickets, inability of renal tubules to absorb phosphate, inability of renal tubules to absorb phosphate, GFR is normal
Impaired vitamin D3 response, X linked dominant
Tibial bowing due to widened proximal tibia physis
Lowered phosphate, increased alk phos
Treat with calcitriol, surgery
Vit D deficiency rickets (nutritional)
Rare now that vit D is added to milk
Still seen in: premature infants, black kids older than 6mo still breastfed, pt with malabsorption syndrome (celiac), asians, parents with unusual dietary choices
Low Vit D –> low intestinal absorption of calcium–> increased PTH and bone resorption–> increased alk phosphatase levels
Clinical findings: rachitic rosary, bowing knee, codfish bertebrae, retarded bone growth, muscle hypotonia, dental disease, path fracture, waddling gait
Low Ca, low phosphate, high alk phos, high PTH, really low 1 25 oh Vit D
hereditary Vit D dependent rickets (type 1 and 2)
Rare, similar to vit D deficient rickets, but more severe
Type 1: joint pain, deformity, hypotonia, muscle weakness, growth failure and hypocalcemic seizures, or fractures, in early in infancy (caused by defect in renal 25 oh vit D1 a-hydroxylase, prevents conversion of inactive form of vit D to active form) high pth, low 1 25 oh vit d
Type 2: bone pain muscle weakness, hypotonia, hypocalcemia, convulsions, growth retardations, sever dental disease (cause: defect in intracellular receptor for 1 25 OH vit D) really high 1 25 oh vit D
Autosomal recessive
osteomalacia
metabolic bone disease where defective mineralization results in large amount of unmineralized osteoid
Qualitative defect as apposed to quant (osteoporosis)
Rickets and osteomalacia are manifestation of the same pathologic process
Presents with: generalized bone and muscle pain, fractures of long bones, ribs, vertebrae, proximal muscle weakness, fatigue
Physical exam: waddling gait, difficulty rising from chair, and climbing stairs
Loosers zone: medial fermoral cortex, pubic ramus, scapula,fractures (especially in proximal femur and neck), biconcave vertebral bodies, protrusio acetabuli
Risk factors of ostemalacia
vit D deficient diets, malabsorption (celiac disease, renal osteodystrophy, hypophosphatemia, chronic alcholism, tumors)
Oncogenic osteomalacia
Paraneoplastic syndrome of renal phosphate wasting
Caused by metastatic tumor, primary bone tumor, soft tissue, tumor (phosphaturic mesenchymal tumor)
Secretes phosphatonin that affect proximal renal tubules, reduces calcitriol production in the kidney and inhibits phosphate transports, leads to increased renal phosphat excretion, hypophosphatemia, osteomalacia
Treatment remove the tumor
Scurvy
Vitamin C deficiency
Risk factors: elderly alcoholic smokers, malabsorptive diseases
Pathophysiology: humans unable to synthesize L ascorbic acid, bc the enzyme L gluconolactone oxidase
Vit C deficiency–> decreased chondroitin sulfatate and collage synthesis and repair
Impaired intracellular hydroxylation of collagen peptides, leads to impaired intracellular hydroxylation of collagen–> impaired bone formation in metaphysis
Sponfiosa of growth plate
Bone pain, myalgia, bleeding, petechiae, joint effusion, swelling over long bones, Rosary
White line of frankel, wimberger ring, pelkin spur and fracture
