osteomalacia

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

• high remodeling rate: excessive osteoid formation with normal/little mineralization
• low remodeling rate: normal osteoid production with diminished mineralization

Epidemiology

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

Clinical presentation

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

Pathology

Etiology

• vitamin D deficiency (most common)
  • inadequate intake or absorption
    • dietary deficiency of vitamin D
    • lack of sunlight exposure
    • gastric surgery (e.g., gastrectomy or gastric bypass)
    • small bowel disease (e.g., Crohn disease, celiac disease)
    • pancreatic insufficiency (e.g. cystic fibrosis)
  • deficiency of vitamin D metabolism
    • cirrhosis (25-hydroxylation of vitamin D)
    • chronic kidney disease (1-hydroxylation of 25-vitamin D)
    • cytochrome P450 inducers (e.g. phenobarbital, antiepileptic drugs)
• phosphate deficiency
  • inadequate intake or absorption
    • antacids
  • renal phosphate wasting
    • hereditary hypophosphatemic rickets
    • Fanconi syndrome
    • tumor-induced (oncogenic) osteomalacia, most commonly due to phosphaturic mesenchymal tumor
• decreased deposition of calcium in bone
  • bisphosphonates (for the treatment of Paget disease)

Markers

• 25(OH)D: decreased
• serum calcium: slightly decreased / normal
• urinary calcium: decreased
• serum phosphorus: decreased
• serum alkaline phosphatase: elevated
• serum parathyroid hormone: elevated

Radiographic features

Musculoskeletal

There can be variable appearances dependent on the cause:

• diffuse demineralization: osteoporotic-like pattern
  • may show a characteristic smudgy "erased" or "fuzzy" type of demineralization
• coarsened trabeculae 
• insufficiency fractures
  • Looser zones
• articular manifestations (uncommon)
  • protrusio acetabuli
  • rheumatoid arthritis-like changes
  • osteogenic synovitis
  • ankylosing spondylitis-like changes

Siehe auch:

• Morbus Paget des Knochens
• Osteoporose
• Insuffizienzfraktur

und weiter:

• Basiläre Impression
• Rachitis
• primärer Hyperparathyreoidismus
• Protrusio acetabuli
• Renale Osteodystrophie
• Superscan Szintigraphie
• Loosersche Umbauzonen
• Sprengel-Deformität
• basilar invagination (mnemonic)
• osteoid
• differential diagnosis of generalized osteopaenia
• generalised osteopaenia
• Platybasie
• Bananen-Fraktur