Osteomalacia Flashcards
Osteomalacia is defective bone m______
mineralisation
What does epiphyseal fusion refer to?
Process by which the epiphysis (rounded end of long bone) fuses with the diaphysis (shaft or main part of bone).
Crucial step in bone maturation.
Epiphysis and diaphysis of long bones separated by growth plate (epiphyseal plate) composed of cartilage.
Responsible for length of growth of bones during childhood and adolescence. New cartilage placed gradually replaced by bone tissue.
Defective one mineralisation before the epiphyseal fusion is called…
rickets
Defective bone mineralisation after the epiphyseal fusion is called…
Osteomalacia
What deficiency causes rickets or osteomalacia?
Vitamin D deficiency (therefore lower calcium and phosphate concentration).
What are different causes of osteomalacia?
HyperPTH
Vitamin D deficiency
CKD/renal failure
Liver failure
Anticonvulsant drugs
Why does hyperparathyroidism cause osteomalacia?
More PTH means more osteoclast activity so more bone resorption.
More calcium and phosphate released into bloodstream contributing to softening of bones.
PTH promotes phosphate excretion by kidneys and indirectly increases absorption of calcium from GI tract.
How does Vitamin D deficiency cause osteomalacia?
Vitamin D is essential for absorption of calcium so lower levels of calcium.
Adequate calcium is needed for proper mineralisation of bone matrix.
To counter the decreased blood calcium, bone resorption may occur contributing to softening of bones.
How does CKD cause osteomalacia?
Kidneys play crucial role in activating vitamin D which is essential in calcium absorption.
Impaired renal function, decreased ability to excrete phosphate leading to hyperphosphatemia. Results in deposition of calcium phosphate in soft tissues instead of being properly incorporated in bone matrix.
What is activated vitamin D called?
Calcitriol
How does liver failure cause osteomalacia?
Liver plays crucial role in making activated vitamin D. It modifies vitamin D after exposure to the sun via the skin. Vitamin D essential for absorption of calcium and phosphate in intestines.
What are symptoms of osteomalacia?
Fractures
Proximal weakness
Difficulty weight bearing
What are symptoms of rickets?
Skeletal deformities:
Knocked knees and bowed legs
Wide epiphyses
How do you diagnose osteomalacia?
Bone marrow biopsy: shows incomplete mineralisation
Bloods: decreased vitamin D, hypocalcaemia, increased PTH, high ALP
X-Ray: Looser’s zones (defective mineralisation)
How do you treat osteomalacia?
Vitamin D replacement (calcitriol) and increased dietary intake of vitamin D
