Osteomalacia (OM) is bone softening due to insufficient mineralisation of the osteoid secondary to any process that results in vitamin D deficiency or defects in phosphate metabolism:

  • high remodelling rate: excessive osteoid formation with normal/little mineralisation
  • low remodelling rate: normal osteoid production with diminished mineralisation

Because of the many causes of osteomalacia worldwide, the epidemiology is highly variable 9

Patients with osteomalacia may be asymptomatic or present with bone pain/tenderness and/or muscular weakness. 

Aetiology
  • dietary deficiency of vitamin D and lack of sunlight exposure
  • deficiency of vitamin D metabolism
    • chronic renal disease (most common cause)
      • 1-hydroxylation of 25-vitamin D
  • chronic liver disease:
    • hepatocellular: 25-hydroxylation vitamin D 
    • biliary: abnormal gut absorption 
    • administration of phenobarbital (alternate liver pathway)
  • decreased absorption of vitamin D
  • decreased deposition of calcium in bone
  • defects in phosphate metabolism
    • phosphate deficiency, e.g. phosphate binders (some antacids), malabsorption
    • familial hypophosphataemia
    • Fanconi syndrome
Markers
  • 25 OH-D: decreased
  • serum calcium: slightly decreased / normal
  • urinary calcium: decreased
  • serum phosphorus: decreased
  • serum alkaline phosphatase: elevated
  • serum parathyroid hormone: elevated
Musculoskeletal

There can be variable appearances dependant on the cause 5:

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Article information

rID: 21389
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:
  • Osteomalacia: general
  • Osteomalacia (OM)

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