Osteomalacia

Question 1

What is osteomalacia

Answer 1

A disorder of mineralisation foo bone matrix (osteoid)

Question 2

What is Rickets

Answer 2

a disorder of defective mineralisation of cartilage in the epiphyseal growth plates of children

Question 3

Describe the aetiology of osteomalacia

Answer 3

Osteoclasts begin the bone remodelling cycle by excavating a cavity on the bone surface
Osteoblasts lay down the organic matrix (osteoid)

Question 4

What are matrix vesicles

Answer 4

Extracellular organelles derived from the plasma membrane of chondrocytes

Question 5

What is defective bone mineralisation in osteomalacia mostly due to

Answer 5

reduced calcium and phosphate elevel sin the extracellular fluid

Question 6

When can primary renal phosphate wasting occur

Answer 6

Renal tubular acidosis
X linked hypophosphataemic rickets
autosomal dominant hypophosphataemic rickets
oncogenic (tumour-induced) osteomalacia

Question 7

How might osteomalacia present radiologically

Answer 7

as osteopenia

Question 8

What might patients with osteomalacia complain of

Answer 8

Diffuse bone pain and tenderness
fractures with little or no trauma
proximal muscle weakness - associated with a waddling gait

Question 9

What are some other skeletal deformities in children with Ricket’s

Answer 9

Frontal bossing
pectus carinatum
bowing of the long bones

Question 10

What investigations should be done for suspected osteomalacia

Answer 10

spine X ray - increased bone density

Looser’s zones or pseudo fractures (characteristic finding)

Question 11

How can osteomalacia be diagnosed

Answer 11

bone biopsy using double tetracycline labelling

Question 12

What is the treatment for osteomalaicia

Answer 12

Reversal of the underlying disorder (eg. gluten free diet)

Supplementation with vitamin D and calcium

Question 13

How are patients with hereditary hypophosphataemic rickets treated

Answer 13

with a combination of oral phosphate supplementation and calcitriol

Question 14

Describe the following in patients with vitamin D deficiency  
Plasma phosphate
plasma calcium 
alkaline phosphatase 
25-hydroxyvitamin D
PTH

Answer 14

Plasma phosphate: low
plasma calcium: low
alkaline phosphatase: increased
25-hydroxyvitamin D: low 
PTH: increased

Question 15

How are patients with hereditary hypophosphataemic rickets treated

Answer 15

a combination of oral phosphate supplementation and calcitriol

Question 16

What often indicates that treatment is effective in hypocalcaemic patients

Answer 16

Maintenance of normal urinary calcium levels