Metabolic Bone Disorders Flashcards
What is renal osteodystrophy?
Bone mineralization defect secondary to electrolyte and endocrine dysfunction
What is the mechanism behind renal osteodystrophy?
Glomerular damage = phosphate retention = hyperparathyroidism
Tubular damage = reduction in 1,25 (OH)2 D3 synthesis
What are Looser’s zones?
Pseudofractures/milkmans fractures
Lucencies with sclerotic borders transversing partway across bone
Definitions of Rickets?
Defect in mineralization of osteoid matrix secondary to inadequate calcium and phosphate with failure of calcification in zone of provisional calcification
What are the 3 types of Rickets
- Vit D deficient
- Vit D dependant
- Vit D resistant (Familial/ Hypophosphatemic)
What is the pathogenesis of Familial/hypophosphatemic/ vit d resistant rickets?
Renal phosphate wasting - inability to resorb
What are the inheritance patterns of FR?
- X linked dominant - MAIN
- Autsomal dominant
- Autosomal recessive
What gene is mutated and effect in x linked dominant FR?
PHEX
Increases FGF 23
What are the two types of Vit D dependant rickets?
RARE AND SEVERE
Type 1 - defect of 1 alpha hydroxylase (ENZYME)
Type 2 - end organ resistance to 1,25 vit d (RECEPTORS)
Like type 1/ type 2 diabetes
What is the pathogenesis of vit D def?
Decreased intake - Nutritional/ No sunlight
Decreased absorption - Malabsorption
Characteristic lab finding in vit D resistant rickets?
Normal Vit D levels
Characteristic lab finding in Vit D def
Low Vit D levels
Low ca/po4
Characteristic lab finding in type 1 vit D dependant?
- V Low Calcitriol levels
Characteristic lab finding in type 2 vit D dependant?
- V High Calcitriol levels
What is the inheritance pattern of hypophosphotasia?
Autosomal recessive