Osteomalacia and Rickets

Question 1

what happens to the bone in osteomalacia/rickets

Answer 1

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

Question 2

rickets or osteomalacia

Answer 2

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

Question 3

clinical features of rickets

Answer 3

growth retardation, hypotonia, apathy in infants

once walking: knock kneed, bow legged and deformities of the metaphyseal epiphyseal junction

features of decreased calcium

Question 4

features of osteomalacia

Answer 4

bone pain and tenderness, fractures, proximal myopathy (muscle wasting - waddling gait)

dental defects - caries and enamel problems

Question 5

causes

Answer 5

vitamin D deficiency

vitamin D resistance

drugs liver disease

renal osteodystrophy

tumour induced osteomalacia

Question 6

vitamin D deficiency causes

Answer 6

• Deficient diet
• Malabsorption- gastric surgery, coeliac, pancreatic failure (dietary vitamin D)
• Cirrhosis
• Lack of sunlight
• Chronic renal failure
  
  • Etc.
    *

Question 7

renal osteodrystrophy

Answer 7

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

Question 8

what drugs can be a cause

Answer 8

eg anticonvulsants (phenytoin)

• induce liver enzymes leading to an increased breakdown of 25 OH vitamin D

Question 9

what is typically seen on x ray in rickets

Answer 9

ragged metaphyseal surfaces and bowing of the long bone

Question 10

what is typically seen on x ray in osteomalacia

Answer 10

note looser zones

Question 11

what is typically seen on x rays of osteomalacia and rickets

Answer 11

looser zones (pseudofractures)

wide transverse lucencies traversing part way through a bone

Question 12

what are pseudofractures

Answer 12

a type of insufficiency fracture

• a result of normal stresses on abnormal bone

Question 13

what are the long term consequences of vitamin D deficiency

Answer 13

bone disease (demineralization/fractures and osteomalacia/rickets)

malignancy (especially of colon), heart disease and diabetes

Question 14

what is the chronic treatment

Answer 14

vitamin D3 tablets

calcitriol

alfacalcidol (1 alpha OH cholecalciferol)

combined calcium and vitamin D eg Adcal D3

Question 15

vitamin D resistant rickets

Answer 15

X-linked hypophosphataemia is an X linked dominant form of rickets

it is due to a defect in renal phosphate handling

Question 16

what mutations are responsible for X-linked hypophosphataemia

Answer 16

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

Question 17

biochemistry of X-linked hypophosphataemia

Answer 17

plasma phosphate is low, ALP high and there is high vitamin D

Question 18

treatment of X-linked hypophosphataemia

Answer 18

high dose oral phosphate and calcitriol

surgery is an option

Question 19

SUMMARY

Answer 19

Question 20

what supplementation should all pregnant and breastfeeding women take

Answer 20

daily supplement of 10 mcg (400 iu) of vitaminD

Question 21

what supplementation should all infants and young children from 6 months to 5 years take

Answer 21

vitamin D daily to meet requirement of 7-8.5 mcg (300iu)

Question 22

does infant formula contain enough vitaminD

Answer 22

over 500ml does

Question 23

what do breastfed infants need if their mother has not taken vitamin D supplements throughout pregnancy

Answer 23

may need vitamin supplements from one month of age

Question 24

what vitamin supplements are available

Answer 24

• abidec multivitamin drops - ABCD
• healthy start - ACD