Osteomalacia and Rickets Flashcards
what happens to the bone in osteomalacia/rickets
there is a normal amount of bone, but its mineral content is low (there is excess uncalcified osteoid and cartilage)
this is the reverse of osteoperosis, in which the mineralization is unchanged, but there is overall bone loss
rickets or osteomalacia
rickets is the result if the process occurs during the period of bone growth
osteomalacia is the result if the process occurs after fusion of the epiphyses
clinical features of rickets
growth retardation, hypotonia, apathy in infants
once walking: knock kneed, bow legged and deformities of the metaphyseal epiphyseal junction
features of decreased calcium
features of osteomalacia
bone pain and tenderness, fractures, proximal myopathy (muscle wasting - waddling gait)
dental defects - caries and enamel problems
causes
vitamin D deficiency
vitamin D resistance
drugs liver disease
renal osteodystrophy
tumour induced osteomalacia
vitamin D deficiency causes
- Deficient diet
- Malabsorption- gastric surgery, coeliac, pancreatic failure (dietary vitamin D)
- Cirrhosis
- Lack of sunlight
- Chronic renal failure
- Etc.
*
- Etc.
renal osteodrystrophy
renal failure leads to calcitriol (1,25 dihydroxy-cholecalcifero) deficiency
- can cause secondary hyperparathyroidism (appropriate increase)
patients may have a high 25 OH vitamin D, but 1-25 must be checked
- titrate treatment to PTH levels, but dont forget phosphate binders
what drugs can be a cause
eg anticonvulsants (phenytoin)
- induce liver enzymes leading to an increased breakdown of 25 OH vitamin D
what is typically seen on x ray in rickets
ragged metaphyseal surfaces and bowing of the long bone
what is typically seen on x ray in osteomalacia
note looser zones
what is typically seen on x rays of osteomalacia and rickets
looser zones (pseudofractures)
wide transverse lucencies traversing part way through a bone
what are pseudofractures
a type of insufficiency fracture
- a result of normal stresses on abnormal bone
what are the long term consequences of vitamin D deficiency
bone disease (demineralization/fractures and osteomalacia/rickets)
malignancy (especially of colon), heart disease and diabetes
what is the chronic treatment
vitamin D3 tablets
calcitriol
alfacalcidol (1 alpha OH cholecalciferol)
combined calcium and vitamin D eg Adcal D3
vitamin D resistant rickets
X-linked hypophosphataemia is an X linked dominant form of rickets
it is due to a defect in renal phosphate handling
what mutations are responsible for X-linked hypophosphataemia
ones involved in renal phosphate handling:
PEX/PHEX genes which encode an endopeptidase
FGF2 gene which regulates phosphate levels in plasma and is secreted by osteocytes in response to calcitriol
biochemistry of X-linked hypophosphataemia
plasma phosphate is low, ALP high and there is high vitamin D
treatment of X-linked hypophosphataemia
high dose oral phosphate and calcitriol
surgery is an option
SUMMARY
what supplementation should all pregnant and breastfeeding women take
daily supplement of 10 mcg (400 iu) of vitaminD
what supplementation should all infants and young children from 6 months to 5 years take
vitamin D daily to meet requirement of 7-8.5 mcg (300iu)
does infant formula contain enough vitaminD
over 500ml does
what do breastfed infants need if their mother has not taken vitamin D supplements throughout pregnancy
may need vitamin supplements from one month of age
what vitamin supplements are available
- abidec multivitamin drops - ABCD
- healthy start - ACD
