Post on 23-Dec-2015
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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– Marrow decreased by bone growth, may cause
pancytopenia.– Extramedullarly haematopoeisis– Cranial nerve compression -> blindness, deafness,
vision loss
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
Paget’s disease (osteitis deformas)• Localised disorder of bone remodelling caused by excessive resorption and 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
Paget’s disease (osteitis deformas)
• X-ray – Bone enlargement with lytic and sclerotic areas.
• Complications– AV shunts within marrow can cause high output
cardiac failure.– Osteosarcoma or other sarcomas.
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
Osteoporosis
• X-ray– General translucency of bone
• Treatment– Oestrogen replacement therapy – controversial– Weight bearing exercise– Calcium and vitamin D– Biphosphonate– Calcitonin
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
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,
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
– Curvative parathyroidectomy
Renal Osteodystrophy• Describes clinically all of the skeletal changes of chronic renal
disease.– Increased osteoclastic bone resorption mimicking osteoitis fibrosa
cystica.– 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
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