Osteomalacia

Question 1

Define Osteomalacia & VitD deficiency

Answer 1

• Osteomalacia is a metabolic bone disease characterised by incomplete mineralisation of osteoid following growth plate closure in adults.
• Vitamin D deficiency is described as a level of VitD < 75nM

Question 2

Explain the aetiology/risk factors of vitamin D deficiency and osteomalacia

Answer 2

• The lack of Vitamin D leads to a lack of mineralisation of osteoid
• LOW PO4: Rare conditions that cause renal phosphate wasting include Fanconi’s syndrome and Oncogenic Osteomalacia
• Vitamin D deficiency can be caused by:
  
  • GI Malabsoprtion: Coeliac, IBD
  • Liver/Renal dysfunction (faulty 1-a-OH /25-a-OH)
  • Dark skin (melanin blocks the UV)
  • Inadequate sunlight (covered up, too much sunscreen)
  • Dietary lack of dairy & fish
  • Drugs (phenytoin, phenobarbital, Carbamezapine)
  • Genetic disorders - RARE
  • Pancreatic insufficiency (lack of Vit D absorption)

Question 3

Summarise the epidemiology of vitamin D deficiency and osteomalacia

Answer 3

• In the US, Europe, and East Asia, more than 40% of the adult population >50 years are vitamin D deficient (lack of sunlight), & is the most prominent cause of osteomalacia.
• In the Middle East, a high prevalence of rickets and osteomalacia has been described in Muslim women and their infants, perhaps due to increased clothing coverage of the skin.

Question 4

Recognise the presenting symptoms of vitamin D deficiency and osteomalacia

Answer 4

• Diffuse Bone pain and tenderness
• Proximal Myopathy
• Malabsorption symptoms

Question 5

Recognise the signs of vitamin D deficiency and osteomalacia on physical examination

Answer 5

• Signs of hypocalcaemia: Trousseau’s & Chvostek’s
• Waddling gait
• Bone tenderness

Question 6

Identify appropriate investigations for vitamin D deficiency and osteomalacia and interpret the results

Answer 6

• Bone x-ray: Looser’s pseudofractures
• Serum Calcium, PTH & PO4: Low/Low Normal Ca 9reduced gut absoprtion), Low PO4 (reduced absorption & contunuing reabsorption), High PTH in response to low Ca
• ALP: High, will be low Hypophosphatasia
• Serum Vitamin D: Should be low (<25nM)
• 24 hour urine Calcium: Will distinguish that this is not CKD causing 2HPT as in VitD def, PTH is still able to increase Ca reabsoprtion so it shiuld not be in urine
• 24 hour urine Phosphate

Question 7

Generate a management plan for vitamin D deficiency and osteomalacia

Answer 7

• Vitamin D (colecalciferol/ergocalciferol) and Calcium supplement
  
  • Give active VitD (alfacalcidol/calcitriol) is renal failure is present
  • Add Phosphate if there is a phosphate wasting syndrome (e.g. Fanconi’s syndrome)

Question 8

Identify the possible complications of vitamin D deficiency and osteomalacia and its management

Answer 8

• Secondary hyperPTH
• Calcium overload can lead to hypercalcaemia & hypercalcuria/nephrocalcinosis
• Pseudofractures in Looser’s zone

Question 9

Summarise the prognosis for patients with vitamin D deficiency and osteomalacia

Answer 9

The clinical outcome is dependent on the underlying cause and compliance with therapies.