Osteomalacia

Question 1

Pathophysiology of OM

Answer 1

a metabolic bone disease characterised by incomplete mineralisation of the underlying mature organic bone matrix (osteoid) following growth plate closure in adults.
Sequential hydroxylation of vitamin D is required to produce the metabolically active form of vitamin D. Hydroxylation occurs first in the liver and then in the kidneys and produces 1,25-dihydroxyvitamin D.

Question 1

What is rickets / osteomalacia

Answer 1

a condition that affects bone development in children. It causes bone pain, poor growth and soft, weak bones that can lead to bone deformities.

Question 2

RF of OM

Answer 2

• suboptimal UV-B sunlight exposure and the use of sunscreen
• insufficient dietary supplementation, and/or
• the inability of the small intestine to absorb adequate amounts of dietary sources of vitamin D.
• Old age
• Fractures
• Hypophosphatasia
• Anticonvulsant therapy

Question 3

Acquired factors that affect OM

Answer 3

• Nutritional deficiencies: vitamin D, phosphorus, and calcium deficiency related to dietary deficiency, malabsorption, or lack of UV-B light exposure
• Drug-induced: anticonvulsants
• Renal osteodystrophy
• Mineralisation inhibitors
• Tumour-induced

Question 4

How do anticonvulsants cause OM

Answer 4

increase the catabolism of vitamin D and reduce intestinal calcium absorption

Question 5

How can CKD MBD cause OM

Answer 5

Hyperphosphataemia in chronic kidney disease-mineral bone disorder directly induces hypocalcaemia and decreases the efficacy of 1-alpha-hydroxylase in the kidney. This, in turn, decreases active vitamin D metabolites and thus the ability of the gut to absorb calcium. Subsequently, secondary hyperparathyroidism develops.

Question 6

How can OM be tumour acquired

Answer 6

an acquired paraneoplastic syndrome of renal phosphate wasting that resembles genetic forms of hypophosphataemic rickets.

Question 7

Symptoms of OM

Answer 7

• Diffuse bone pain and tenderness
• Fractures
• Malabsorption syndromes
• Proximal muscle weakness
• Waddling gait.

Question 8

PE for OM

Answer 8

The physical examination is remarkable for bone tenderness to percussion, poorly localised bony tenderness, and proximal muscle weakness. Pain in the hips may result in a waddling gait.

Question 9

Ix for OM

Answer 9

• Serum calcium - low
• Serum 25-hydroxyvitaminD levels - low
• Serum phosphate - low
• Serum urea and creatinine - ratio is elevated.
• Intact PTH - High
• ALP - high except in those with hypophosphatasia
• 24-hour urinary calcium - low

Question 10

Definitive Ix for OM

Answer 10

Iliac crest biopsy using double tetracycline labelling is the definitive diagnostic test; however, due to the invasive nature, it is rarely performed.

Question 11

Treatment OM

Answer 11

Calcium + Vit D - Ergocalciferol or cholecalciferol AND calcium carbonate or calcium citrate.

Question 12

Lifestyle factors to treat OM

Answer 12

Ensuring adequate sunlight exposure and dietary intake of fortified foods containing vitamin D, calcium, and phosphorus may help avoid osteomalacia.

Question 13

Ddx OM

Answer 13

• Osteoporosis
• Pagets

Question 14

Difference between OM and OP on Xray

Answer 14

Indistinguishable

Question 15

Monitoring of treatment of OM

Answer 15

A patient’s 25-hydroxyvitamin D levels should be checked approximately 2 to 3 months after initiating therapy. If undergoing long-term treatment, adults require ongoing annual monitoring for signs and symptoms of osteomalacia and over-treatment with vitamin D.

Question 16

Complications of OM

Answer 16

Fractures and fragility.