deck_Metabolic bone disorders Flashcards
What are the disease of impaired bone mineralization ?
Rickets and Osteomalacia
What are the etiologies of osteomalacia and Rickets ?
- Vitamin D deficiency due to poor direct, low sun exposure or malabsorption due to Coeliac or Crohn’s disease.* Liver disease- Impaired conversion of Cholecalciferol to Calcidiol. * Kidney disease- Which impairs conversion of Calcidiol to Calcitriol. * Iatrogenic – Phenytoin* Tumour-induced osteomalacia – tumour production of FGF23 whichinhibits conversion from Calcidiol to Calcitriol.* Vitamin D Resistance – inherited disorder
What is the presentation of osteomalacia and Rickets ?
They presents with * Diffuse bone and joint pain* Proximal muscle weakness* Bone fragility* Fractures from minor trauma* Muscle spasms/cramps
What are the signs seen in Rickets ?
- Craniotabes* Delayed closure of fontanelles* Genu varum* Prominent frontal bone* Protruding abdomen* Rachitic Rosary
What are the laboratory findings in Rickets and Osteomalacia ?
- Low serum Vitamin D levels* Low Calcium* Elevated Alkaline Phosphatase* High Parathyroid Hormone (PTH) due to Low serum Phosphate
What are the radiological finding in osteomalacia and Rickets ?
Looser Zones which are cortical infarctions and Milkman’s lines which are Psuedo fractures.
What are the characteristic radiological findings in Rickets ?
Metaphysial widening of long bones and frayed metaphisial edges due to poor mineralization of the growth plates.
What is the Tx for Osteomalacia and Rickets ?
Treat underlying cause, if it is Vitamin D deficiency Oral Vitamin D▪ Daily replacement of vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol)▪ High dose (1000 – 6000 IU per day depending on age) for three months▪ Maintenance dosing thereafter (400 – 600 IU per day depending on age)Calcium supplementation▪ 30-50 mg/kg body weight per day (diet or supplements)* Resolution of biochemical and radiologic abnormalities should occur within 3 months of therapy
What is the aetiology of Paget’s disease?
The exact aetiology is unknown genetic and viral aetiologies are suspected.
What are the three phases of Paget’s disease ?
- I – Lytic Phase: Abnormal osteoclasts demonstrate aggressivedemineralization of bone, creating lytic lesions in bone* II – Mixed Phase: Mixed between lytic and blastic phases; abnormalnumber of osteoblasts begin to lay down bone rapidly in a disorganizedmanner* III – Sclerotic Phase: Bone formation exceeds bone resorption creatingstructurally disorganized and weak bones
What is the dormant state of Paget’s disease ?
It is a state in which osteoblast and osteoclast activity is slowed orhalted.
What are the risk factors for Paget’s disease ?
- Genetics / family history of disease* Age > 40 years old* Western European descent
What is the Tx of Paget’s disease ?
- Pain can be managed with NSAIDS* Bone lysis can be managed with bisphosphonates, Vitamin D and Calcium. * Surgical correction of nerve impingements may be needed.
What is the laboratory indicator of Paget’s disease Tx success ?
ALP level normalisation.
What is the pathophysiology of renal osteodystrophy ?
It is a disorder of the bone mineral homeostasis occurs secondary to CKD. CKD causes hyperphosphatenemia, which is initially off-set by increasing serum calcium from bone resorption resulting in bone weakness. The CKD also causes impaired conversion of calcidiol into calcitriol leading to impaired absorption of dietary calcium and hypocalcemia. Hypocalcemia occurs later in the disease. Declining kidney function, declining calcitriol production andhypocalcemia lead to higher releases of PTH which leads to increased bone resorption andweakened bones in order to release calcium into the blood resulting in renal osteodystrophy.
