Osteomalacia

Question 1

What is osteomalacia?

Answer 1

Defective bone mineralised leading to there being a normal amount of bone but this bone has a low mineral content -> leads to it being soft

I.e. poor calcification causing a delay or failure of bone matrix mineralisation

Question 2

What is the pathophysiology of osteomalacia?

Answer 2

Vitamin D deficiency results in:
-decreased calcium and phosphate reabsorption in intestines and kidneys

Lack of calcium and phosphate leads decreased bone construction as both components required for osteoblasts to model new bone

Low calcium also stimulates parathyroid gland leading to hyperparathyroidism

• leads to increased osteoclast activity
• causes further problems with bone mineralisation

Question 3

What are other causes of osteomalacia apart from vitamin D deficiency?

Answer 3

Renal osteodystrophy
-renal failure causes decreased activation of vitamin D so causes apparent vitamin D deficiency

Drug-induced
-anti-convulsants can induced liver enzymes which then break down vitamin D

Vitamin D resistance

Liver disease
-decreased hydroxylation of 25-VD + poor VD absorption

Tumour-induced osteomalacia

Question 4

How might someone with osteomalacia present?

Answer 4

May be asymptomatic

Fatigue

Muscle weaknes

Muscle aches

Abnormal fractures

Question 5

What are “looser zones”?

Answer 5

Fragility fractures only going partially through the bone

Question 6

What risk factors might their be for osteomalacia?

Answer 6

Think about the risk factors for vitamin D deficiency

• darker skin
• low exposure to sunlight
• colder climates
• spend a lot of time inside

Question 7

What investigations can be done if osteomalacia is suspected?

Answer 7

Measure serum 25-hypdroxyvitamin D
<25 nmol/L= deficiency

Low Serum calcium

Low Serum phosphate

LFT = Raised ALP

PTH-> look for secondary hyperparathyroidism

Xrays
-osteopenia i.e. bones appear more radiolucent

DEXA = shows low bone mineral density

Question 8

What are the management options for osteomalacia?

Answer 8

Replace Vit D= colecalciferol

• correct initial vitamin D deficiency
• maintenance vitamin D (800 IU)

Question 9

What is rickets?
How does it differ from osteomalacia?
How might someone with rickets present?

Answer 9

Osteomalacia which occurs beform the epiphyses close
I.e. same disease process but occurs at different times = CHILDHOOD

Bowing of legs 
Knock knees 
Rachitic rosary (expansion of costochondral junctions) 
Soft skill -> delayed closure of suture 
Delayed teeth