Osteomalacia

Question 1

What is osteomalacia?

Answer 1

disorder of mineralisation of bone matrix (osteoid) following growth plate closure in adults.

Question 2

What is Rickets?

Answer 2

defective mineralisation of the epiphyseal growth plate cartilage in children

Question 3

Give 3 common causes of Vitamin D deficiency

Answer 3

Lack of sunlight exposure
Dietary deficiency
Malabsorption (Small bowel disease e.g. IBD)

Question 4

Give 3 less common causes of Vitamin D deficiency

Answer 4

Decreased 25-hydroxylation of vitamin D e.g. liver disease
Decreased 1-alpha-hydroxylation e.g. CKD
Vitamin D resistance

Question 5

What 2 broad aetiologies cause osteomalacia?

Answer 5

Vitamin D deficiency

Renal phosphate wasting

Question 6

What are the 4 causes of renal phosphate wasting?

Answer 6

Fanconi’s syndrome
Renal tubular acidosis
Hereditary hypophosphataemic rickets
Tumour induced osteomalacia

Question 7

Describe the epidemiology of osteomalacia

Answer 7

Uncommon in industrialised countries

F > M

Question 8

Give 3 symptoms of osteomalacia

Answer 8

Bone pain (esp Axial skeleton)
Weakness
Malaise

Question 9

Give 7 signs of rickets

Answer 9

Hypotonia
Growth retardation
Skeletal deformities
Bossing of frontal/ parietal bones
Swelling of costochondral junctions (Rickety rosary)
Bow legs
Short stature

Question 10

Give 4 signs of osteomalacia

Answer 10

Bone tenderness
Proximal muscle weakness
Waddling gait
Signs of hypocalcaemia

Question 11

Give 2 specific signs of hypocalcaemia

Answer 11

Trousseau’s sign: Inflation of BP cuff > SBP for > 3 mins causes tetanic spasm of wrist + fingers
Chvostek’s sign: Tapping over facial nerve causes twitching of ipsilateral facial muscles

Question 12

What bloods should be taken in osteomalacia

Answer 12

Low/ normal Ca2+
Low Phosphate
Low hydroxy Vitamin D
High ALP
High PTH (secondary hyperparathyroidism)
U+Es (deranged in CKD)
ABG (possible hyperchloraemic metabolic acidosis)

Question 13

What may be seen on radiographs in osteomalacia?

Answer 13

Normal/ Osteopenic

Looser’s zones (pseudofractures) in ribs, scapula, pubic rami or upper femur

Question 14

What special test can be used in osteomalacia? What does this show?

Answer 14

Bone biopsy after double tetracycline labelling
Deposits at mineralisation front as a band
After 2 courses, distance between bands deposited is reduced (as not mineralising bone)

Question 15

Describe the management of osteomalacia

Answer 15

Vitamin D + Calcium replacement

Monitor 24hr urinary Ca2+, serum Ca2+, phosphate, ALP, PTH + Vitamin D

Question 16

What steps may help address the underlying cause?

Answer 16

Advice on diet

Advice on sunlight exposure

Question 17

How is X linked hypophosphatemia treated?

Answer 17

Oral phosphate + 1,25-dihydroxy Vitamin D

Question 18

List complications of osteomalacia

Answer 18

Bone deformities

Hypocalcaemia: epileptic seizures, cardiac arrhythmias, tetany + depression

Question 19

What is the prognosis in osteomalacia?

Answer 19

Sx + radiological appearances improve with vitamin D tx

Bone deformities in children are permanent