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Metabolic bone diseases

Metabolic bone diseases. There is a clinical problem?. Osteopertrosis. Hereditary decreased osteoclastic function. Decreased resoprtion leads to thick sclerotic bones. Pathology Problems with the osteoclast resorption pit Increased bone density -> thick brittle bones -> fracture

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Metabolic bone diseases

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  1. Metabolic bone diseases There is a clinical problem?

  2. Osteopertrosis • Hereditary decreased osteoclastic function. Decreased resoprtion leads to thick sclerotic bones. • Pathology • Problems with the osteoclast resorption pit • Increased bone density -> thick brittle bones -> fracture • Marrow decreased by bone growth, may cause pancytopenia. • Extramedullarlyhaematopoeisis • Cranial nerve compression -> blindness, deafness, vision loss

  3. Osteopetrosis • X ray • Osteosclerosis, long bones -> Erlenmeyer flask shaped deformity • Clinical features • Autosomal recessive (malignant) • Infants and children, multiple fractures, early death • Autosomal dominant (benign type) • Adults, fractures, mild anaemia, cranial nerve impingement • Carbonic anhydrase II deficiency • Renal tubular acidosis, cerebral calcificaiton • Treatment • Bone marrow transplant

  4. Paget’s disease (osteitisdeformas) • Localised disorder of bone remodelling caused by excessive resorptionand disorganised replacement leading to thickened but weaker bone. • Epidemiology – begins after age 40, european ancestry • Etiology – possible genetic predisposition, possibly paramyxovirus • Forms of involvement • Monostotic (15%), polystotic (85%) • Commonly – skull, pelvis, femur, vertebrae • Pathology • Three stages • Osteolytic – otseoclastic activity predominates • Mixed osteoclastic and osteoblastic • Osteosclerotic – osteoblastic activity predominates -> burnout stage • Micro haphazard arrangement leads to mosiac pattern of lamellar bone • Bone is weak, fractures easily • Skull involvement • Increase in head size • Foraminal narrowing leading impingement of the cranial nerves • Facial bones can be involved leading to a lion like face

  5. Paget’s disease (osteitisdeformas) • X-ray • Bone enlargement with lytic and sclerotic areas. • Complications • AV shunts within marrow can cause high output cardiac failure. • Osteosarcoma or other sarcomas.

  6. Osteoporosis • Osteopenia • Epidemiology • Most common bone disease • Elderly, post menopausal • Pathogenesis • Primary………………………. • Secondary………………….. • Clinical features • Bone pain and fractures • Weight bearing bone predisposed to fracture • Loss of height and kyphosis

  7. Osteoporosis • X-ray • General translucency of bone • Treatment • Oestrogen replacement therapy – controversial • Weight bearing exercise • Calcium and vitamin D • Biphosphonate • Calcitonin

  8. Osteomalacia and Rickets • Decreased mineralisation of newly formed bones, usually caused by deficiency or abnormal metabolism of vitamin D. • Etiology – deficiency of vit D, intestinal malabsorption, lack of sunlight, renal or liver disease. • Epidemiology • Osteomalacia – adults • Rickets - children

  9. Osteomalacia and Rickets • Pathogenesis • Osteomalacia -> poor mineralisation of newly formed bone -> thin fragile bones -> fracture • Rickets • Remodelled bone and bone at growth plates are undermineralised • Endochondral bone formation also affected -> deformity • Fractures also occur • Clinical presentation • Osteomalacia -> bone pain, fracture (vertebrae, hips, wrist) • Rickets -> bow legs, craniotabes, lumbar lordosis,

  10. Hyperparathyroidism • Primary • Adenoma or autonomous hyperplasia (Robbins) • Secondary • Caused by prolonged states of hypocalcemia leading to hyperplasia • Tertiary? • Autonomous hyperplasia • Severe cases lead to osteitis cystic fibrosa (no longer though…) • Presentation • Asymptomatic hypercalcamia • Treatment • Curvativeparathyroidectomy

  11. Renal Osteodystrophy • Describes clinically all of the skeletal changes of chronic renal disease. • Increased osteoclastic bone resorption mimicking osteoitisfibrosacystica. • Delayed matrix mineralisation. • Osteosclerosis. • Growth retardation. • Osteoporosis. • Main types • High turnover -> increased resorption and bone formation (dominates) • Low turnover (aplastic) -> adynamic bone, less commonly osteomalacia

  12. Renal Osteodystrophy • Pathogenesis (long..) • Chronic renal failure results in phosphate retention and hyperphosphatemia • Hyperphospatemia induces secondary hyperparathyroidism (via regulating PTH secretion) • Hypocalcaemia develops due vitamin D problems (kidneys) • PTH secretion markedly increases at all levels of serum calcium • In renal failure decrease in the binding of 1,25-(OH)2D3 to parathyroid cells • Decreased degradation and excretion of PTH (kidneys) • Secondary hyperparathyroidism produces increased osteoclastic activity • Metabolic acidosis associated with renal failure leads to bone resorption

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