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Osteomalacia

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Topic updated on 08/02/16 10:58pm
Introduction
  • A metabolic bone disease where defective mineralization results in a large amount or unmineralized osteoid
    • qualitative defect as opposed to a quanitative defect like osteoporosis
    • rickets and osteomalacia are manifestations of the same pathologic process
  • Epidemiology
    • incidence
      • rare in the US (approximately 1 in 1000)
        • much less common than osteoporosis
        • because of adequate exposure to sunlight and dairy products fortified with vitamin D
    • demographics
      • rickets is found in children (open physis)
      • osteomalacia is found in adults (closed physis)
    • risk factors
      • the following conditions predispose a patient to osteomalacia
        • vitamin-D deficient diets
        • malabsorption e.g. celiac disease
        • renal osteodystrophy
        • hypophosphatemia
        • chronic alcoholism
        • tumors (tumor-induced osteomalacia, see below)
        • drugs 
          • drugs associated with vitamin D deficiency
            • phenytoin
            • phenobarbital
            • rifampin
            • cholestyramine
            • cadmium
            • glucocorticoids
          • drugs affecting phosphate homeostasis
            • aluminium-containing phosphate-binding antacid
            • ifosfamide
          • drugs affecting bone mineralization
            • aluminium
            • etidronate
            • fluoride
Presentation
  • Symptoms
    • generalized bone and muscle pain
    • fractures of long bones, ribs and vertebrae
    • proximal muscle weakness weakness
    • fatigue
  • Physical exam
    • inspection
      • waddling gait
        • from hip pain and thigh weakness
      • difficulty rising from chair and climbing stairs
Imaging
  • Radiographs
    • findings
      • Looser's zones (insufficiency fractures 
        • medial femoral cortex
        • pubic ramus  
        • scapula
      • fractures (especially in the proximal femur/femoral neck)  
      • biconcave vertebral bodies
      • trefoil pelvis
      • protrusio acetabuli  
  • Bone scan
    • findings
      • increased activity
Studies
  • Labs
 
Serum Ca
Serum P
Alk phos
PTH
25-(OH)vit D
1,25-(OH)vit D
Urinary Ca
Osteomalacia 
low 
low
high
high
low
low
low
Osteoporosis normal normal variable normal normal  normal  normal 
Tumor induced osteomalacia low very low low low low low low
Osteopetrosis normal normal high normal normal normal normal
  • Histology
    • requires transiliac biopsy for definitive diagnosis
Histology
Treatment
  • Nonoperative
    • large doses of oral vitamin D (1000IU/day), treat underlying cause
      • indications
        • most patients
    • technique
      • specific subgroups of patients
        • on long-term anticonvulsant therapy
          • supplement with 400-800IU/day of vitamin D
        • with hepatobiliary disease
          • supplement with 25(OH)-vit D
        • with renal disease
          • supplement with 1,25(OH)2 vit D

 

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