Osteomalacia (MSK)

Question 1

Define osteomalacia.

Answer 1

Softening of the bones secondary to low vitamin D levels which in turn leads to decreased bone mineral content

(Metabolic bone disease characterised by incomplete mineralisation of the underlying mature organic bone matrix (osteoid) following growth plate closure in ADULTS)

Question 2

What is rickets?

Answer 2

Disorder of impaired mineralisation of cartilaginous growth plates in CHILDREN

Question 3

What are the causes of osteomalacia? (3)

Answer 3

• vitamin D deficiency:
  
  • reduced exposure to sunlight
  • low dietary intake
  • reduced intestinal absorption - Coeliac disease, chronic pancreatitis
• defective vitamin D metabolism - liver cirrhosis, CKD
• drugs (anticonvulsants)

Question 4

What does vitamin D deficiency lead to in adults vs children?

Answer 4

• adults - osteomalacia
• children - rickets
• rickets and osteomalacia are different manifestations of the same underlying pathological process

Question 5

What are the clinical features of osteomalacia? (6)

Answer 5

• bone pain and tenderness
• pathological fractures - especially at femoral neck
• proximal myopathy - may lead to waddling gait
• fatigue and weakness
• malaise
• hypocalcaemia symptoms - CATs go numb

Question 6

What are the symptoms of hypocalcaemia (osteomalacia)?

Answer 6

CATs go numb:

• Convulsions
• Arrhythmias
• Tetany
• Paraesthesia

Question 7

What signs of hypocalcaemia might you see in osteomalacia? (2)

Answer 7

• Chvostek’s sign - tapping over facial nerve causes twitching of ipsilateral facial muscles
• Trousseau’s sign - inflation of BP cuff to above SBP for >3mins causes tetanic spasm of wrist and fingers

Question 8

What are the clinical features of rickets? (4)

Answer 8

• hypotonia
• growth retardation
• skeletal deformities
• bow-legged (early childhood), knock knees (later childhood)

Question 9

What are some risk factors for osteomalacia? (6)

Answer 9

• dietary calcium and vitamin D deficiency
• CKD
• limited sunlight exposure
• inherited disorders of vitamin D and bone metabolism
• hypophosphatasia
• anticonvulsant therapy

Question 10

What are the first-line investigations for osteomalacia? (6)

Answer 10

• serum 25-hydroxyvitamin D (low)
• serum calcium (low)
• serum phosphate (low)
• serum ALP (raised)
• intact PTH (raised - secondary hyperparathyroidism)
• serum urea and creatinine (ratio elevated in renal failure)

Question 11

What might you find on an XR in osteomalacia?

Answer 11

• Looser’s zones (pseudofractures)
• may see characteristic findings of long-standing secondary hyperparathyroidism, reversible with treatment
• may show osteopenia
• may appear normal

Question 12

What are some differential diagnoses for osteomalacia? (2)

Answer 12

• osteoporosis - painless and insidious until a fracture develops, advancing age and high-dose glucocorticoids, normal Ca/PO4/ALP/vitamin D/PTH, bone biopsy
• Paget’s disease - ASx, markedly raised ALP, XR

Question 13

What is the main management for osteomalacia?

Answer 13

Vitamin D + calcium replacement:

Ergocalciferol + calcium carbonate

Question 14

How do we manage osteomalacia if renal disease or vitamin D resistance?

Answer 14

Alfacalcidol (1a-hydroxyvitamin D3) or calcitriol (1,25-hydroxyvitamin D3)

Question 15

How do we manage inherited/acquired disorders of phosphate wasting or oncogenic osteomalacia?

Answer 15

Calcitriol + calcium carbonate + sodium phosphate

Question 16

What are some complications of osteomalacia? (4)

Answer 16

• pseudofractures
• hypercalcaemia
• secondary hyperparathyroidism
• hypocalcaemia symptoms - CATs go NUMB

Question 17

What is prognosis of osteomalacia dependent on? (2)

Answer 17

• underlying cause
• compliance with therapies