Osteomalacia

Question 1

Define vitamin D deficiency and osteomalacia?

Answer 1

Osteomalacia is a 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 defective mineralisation of cartilage in the epiphyseal growth plates of children

Question 3

outline the aetiology of vitamin D deficiency?

Answer 3

• vitamin D deficiency
• renal osteodystrophy- cause 1,25-dihydroxycholecalciferol deficiency
• drug induced-anticonvulsants may induce liver enzymes causing increased breakdownof 25hydroxyvitD
• Renal phosphate wasting - syndrome in which there excess urinary phosphat loss

Question 4

what are the causes of vitamin D deficiency?

Answer 4

• lack of exposure to sunlights
• dietary deficiency
• malabsorption
• decrease 25 hydroxylation of vitamin D ( due to liver disease, anticonvulsants)
• decrease 1 alpha- hydroxylation of vitamin D ( due to chronic kidney disease, hypoparathyroidism)
• vitamin D resistance

Question 5

what are the symptoms of renal phosphate wasting?

Answer 5

low serum phosphate causes mylagia and weakness

Question 6

what are the causes of renal phosphate wasting?

Answer 6

• Fanconi syndrome
• renal tubular acidosis ( type 2)
• Hereditary hypophosphatemic rickets ( X linked or autosomal dominant)
• Tumour induced osteomalacia ( Oncogenic hypophosphataemia ) raised tumour,

Question 7

what is Fanconi’s syndrome?

Answer 7

GAP

• phosphaturia
• glycousria
• amino aciduria

Question 8

summarise the epidemiology of vitamin D deficiency and osteomalacia?

Answer 8

common in INUDSTRALISED COUNTRIES

more common in FEMLAES

Question 9

what are the presenting symptoms of osteomalacia?

Answer 9

• bone pain ( mainly in the axial skeleton) and tenderness
• fractures esp femoral neck
• proximal myopathy - waddling gait
• weakness
• malaise

Question 10

what are the symptoms of rickets?

Answer 10

• hypotonia
• growth retardation
• skeletal deformities
• knock need, bowed leg

Question 11

what are the signs of osteomalacia on physical examination?

Answer 11

o Bone tenderness

o Proximal muscle weakness

o Waddling gait

o Signs of hypocalcaemia- TROUSEA’S SIGN AND CHVOSTEK’S SIGN

Question 12

what are the signs of hypocalcaemia on physical examination?

Answer 12

Trousseau’s sign

• inflation of a blood pressure cuff to above the systolic pressure for > 3 mins causes tetanic spasm of the wrist and fingers

Chvostek’s sign

• tapping over the facial nerve causes twitching of the ipsilateral facial muscles

Question 13

what are the signs of rickets on physical examination?

Answer 13

• Bossing of frontal and parietal bones
• Swelling of costochondral junctions (rickety rosary)
• Bow legs in early childhood
• ‘Knock knees’ in later childhood
• Short stature

Question 14

describe the radiograph in osteomalacia

Answer 14

• May appear normal
• May show osteopaenia
• Looser’s zones = wide, transverse lucencies traversing part way through a bone, usually at right angles to the involved cortex and are associated most frequently with osteomalacia and rickets (AKA pseudofractures)

Question 15

describe bone biopsy after double tetracycline labelling?

Answer 15

• tetracycline is deposited at the mineralisation front as a band
• after 2 course of tetracycline ( separated by a few days)- distance between bands of deposited tetracycline is reduced in osteomalacia- incomplete mineralisation

Question 16

what are the appropriate investigations for vitamin D deficiency and osteomalacia?

Answer 16

BLOODS

• low or normal Ca2+
• low phosphate
• High ALP
• low 25-hydroxy vit D- except in vit D resistance
• High PTH ( secondary hyperparathyroidism)
• check U and Es
• check ABG for renal tubular acidosis
• increased phosphate excreting (in renal phosphate wasting)

( consider radiograph and bone biopsy after double tetracycline labelling)

Question 17

outline a management plan for vitamin D deficiency and osteomalacia?

Answer 17

• Vit D and calcium replacement- if dietary deficient
• in malabsorption/ hepatic disease- give Vit D2 ( ergocalciferol)
• In renal disease or vit D resistance- give alfacalcidiol ( 1-hyrdoxyvitD3) or calcitriol ( 1,25-dihydroxyvitD3)

- monitor plasma calcium, initially weekly and if nausea and vomiting

• also monitor serum calcium, phosphate, ALP, PTH, vit D

Question 18

what are the possible complications of vit D deficiency and osteomalacia?

Answer 18

Bone deformities

Hypocalcaemia can cause epileptic seizures

Cardiac arrhythmias

Hypocalcaemic tetany

Depression

Hypocalcaemia symptoms = CATs go NUMB

• Convulsions
• Arrhythmias
• Tetany
• NUMBness/paraesthesia

Question 19

How can you remeber the symptoms of hypocalcaemia?

Answer 19

CATs go NUMB

• convulsions
• arrythmias
• tetany
• numbness/ parasthesia

Question 20

summarise the prognosis for vit D deficiency and osteomalacia?

Answer 20

symptoms and radiological appearances improve with vit D treatment

done deformities in children tend to be permanent