Osteomalacia and Rickets Flashcards
What is osteomalacia?
Disorder of adults characterized by inadequate mineralization of new formed bone matrix
What are rickets?
Disorder of children characterized by inadequate mineraliztaion of newly formed bone matrix and open growth plates
What is the key determinant of formation of 1,25(OH)2D?
Blood calcium concentration
Three causes of hypovitaminosis D?
- Inadequate sunlight exposure
- Deficient dietary intake
- Defective intesttinal absorption
What are the two causes of rickets?
Dietary Vit D deficiency and inadequate sun exposure
Most frequent causes of osteomalacia in the US?
Intrinsic diseases of the small intestine, cholestatic disorders of the liver, biliary obstruction and chronic pancreatic insufficency
What is the underlying pathology in Vit D-dependent rickets type I?
Inherited deficiency in renal 1Alpha-hydroxylase
What is the underlying pathology in Vit D-dependent rickets type II?
Mutation of the vit D receptor so end organs are insensitive to vit D
What is the underlying pathology that leads to osteomalacia in renal disorders?
Impaired reabsorption of phosphate by the proximal renal tubules resuling in hypophosphatemia
What is the cause of vitamin D-resistant rickets?
Mutation in the PHEX gene on the X chromosome impairing transport of phosphate across the luminal membrane of PCT of the kidney
What histologic finding is often found in patient with X-linked hypophosphatemia?
Halos - hypomineralized areas surrounding osteocytes
How can Fanconi Syndrome lead to osteomalacia and rickets?
Inability to reabsorb phosphate and inability to mineralize
How can cancer cause osteomalacia?
Tumors secrete phosphatonins causing renal tubular phosphate wasting resulting in osteomalacia
What is the name of pseudofractures found in osteomalacia?
Milkman-Looser Syndrome
What is the microscopic finding resulting from defective mineralization in osteomalacia?
Exaggeration of osteoid seams in thickness and proportion of trabecular surface coverage
