Osteomalacia

Definition: The osteomalacia can be defined as a metabolic bone disease characterized by defective mineralization (Qualitative defect in Osteomalacia vs. Quantitative defect in Osteoporosis) leading to greater amount of unmineralized osteoid.
The pathology of Osteomalacia is similar to Rickets in children.

Etiopathogenesis: Both rickets and osteomalacia are manifestations of vitamin D deficiency or its abnormal metabolism.
The fundamental defect is an impairment of mineralization resulting into accumulation of unmineralized matrix.

CAUSES/ETIOLOGY:

• Dietery deficiency of vitamin-D
• Malabsorption Syndrome e.g. celiac disease
• Renal osteodystrophy (impaired conversion of 25-vit D to 1,25-vit D)
• Hypophosphatemia
• Chronic alcoholism
• Tumors (Oncogenic osteomalacia)
• Drugs:
  1)drugs causing deficiency of Vit D
  -Phenytoin
  -Phenobarbital
  -Rifampin
  -Cholestyramine
  -Cadmium
  -Glucocorticoids
  2)Drugs altering phosphate homeostasis
  -Aluminium-containing phosphate-binding antacid
  -Ifosfamide
  3)Drugs affecting bone mineralization
  -Aluminium
  -Etidronate
  -Fluoride

Clinical features:

• Symptoms

-Generalized bone & muscle pain
-Low back pain
-Proximal muscle weakness
-Fragile bones (Fractures of long bones, ribs & vertebrae)
-Fatigue, Lethargy
• Signs:
  -Waddling gait(due to thigh muscle weakness & hip pain)
  -Marked adductor spasm
  -Difficulty in rising from chairs & going upstairs
  -Spinal tenderness to percussion
• Radiological features:
  -Looser’s zones/Pseudo-fractures(lucent band of decreased cortical density, perpendicular to bone surface, often multiple, & with/without callus formation) of superior and inferior pubic rami, femoral cortex-medially, scapula, etc.
  -Long bone fractures, e.g. femoral neck fracture.
  -Biconcave vertebral bodies
  -Protrusio acetabuli
  -Deformed pelvis- Triradiate pelvis
• Blood Investigations:
  -Low ⇊ S. Ca, Phosohate. Vit-D level (both 25- & 1,25-vit D)
  -High ⇈ s. ALP, PTH
• DEXA scanning: Low bone density.
• Histological examination: tissue taken by transiliac biopsy(usully not done)
  -wide osteoid seams
  -comparatively larger amounts of unmineralized osteoid

Treatment:

1. Vitamin-D supplementation:
   –Bolus dose– Calciferol, 10,000 IU daily or 60,000 IU weekly, will lead to restoration of body stores of vitamin D over 8 to 12 weeks.
   –Maintenance dose– 1,000-2,000 IU calciferol daily or 10,000 IU weekly is adequate.
   -In adults with severe Malabsorption syndrome, an IM injection of 300,000 IU calciferol monthly for three months then the same dose every 6 months or once a year may be considered.
   (Vitamin-D contraindication- in pt with hypercalcaemia or metastatic calcification. Relative contra-indications- in primary hyperparathyroidism, renal stones, & severe hypercalciuria; Caution with Thiazides & Digoxin)
   -with hepatobiliary disease supplement with 25(OH)-vit D
   -with renal disease supplement with 1,25(OH)2 vit D
2. Treatment of uderlying cause
3. Non-surgical & surgical treatment of fractures & deformity

Also see-
Vitamin D Deficiency including Osteomalacia and Rickets
Osteomalacia