Osteomalacia causes, pathogenesis, diagnosis and treatment

Here is a discussion of Osteomalacia regarding its definition, causes, pathogenesis, clinical pictures, investigations and treatment .
• Osteomalacia is characterized by defective bone mineralization, bone pain, muscle weakness and pathological fractures.
• There is failure to replace the turn over of Ca and P in bone matrix ===> bone become demineralised and the bony substance becomes replaced by soft osteoid tissue so it is mainly a qualitative bone defect.

How Osteomalacia develops ?

Pathogenesis of Osteomalacia
The most common cause is vitamin D deficiency, the low levels of vitamin D causes a reduction of calcium absorption from the intestine.
The low calcium absorption stimulates parathyroid hormone secretion which restores serum calcium levels towards normal by increasing bone resorption and renal tubular calcium reabsorption. The level of parathyroid hormone also promotes phosphaturia and causes phosphate depletion. It is the combination of
calcium loss from bone and phosphate depletion that leads to impaired bone mineralization .

Causes of osteomalacia

Vit. D deficiency
- Dietary decreased  intake
- Lack of synthesis in skin.
- Decreased absorption.
- Defective metabolism
- Anticonvulsants
- Chronic Renal Failure  CRF
Low P with normal vit.D
- Familial hypophosphatemic rickets.
-  Renal tubular disease.
• ·Osteomalacia with normal Ca, P and vit.D
- Hypophosphatasia
- Fibrogenesis imperfecta.
- Aluminium bone disease.

Clinical picture

• Skeletal discomfort (from bone and muscle pain).
• Bone tenderness . Tetany may be manifested.
• Muscular weakness with marked proximal myopathy with waddling gait.
(Osteomalacia is the adult counterpart of rickets).

Investigations to diagnose Osteomalacia

Serum Ca : Low . Serum P : Low  but ++ in CRF
Alkaline phosphatase : ++ , parathyroid hormone: ++ , Low vitamin D level.
X ray :  bone rarefaction with translucent band (pseudofraction or looser's zones) i.e linear areas of low density surrounded by sclerotic borders.

Treatment of Osteomalacia

• Treatment of the cause.
• Vit. D, Ca supplements.
• Diet e.g milk, cheese or yoghurt
• Alfacalcidol especially in cases of renal failure.
Osteomalacia causes, pathogenesis, diagnosis and treatment
Dr.Tamer Mobarak


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