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
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Epidemiology
Because of the many causes of osteomalacia worldwide, the epidemiology is highly variable 9.
Clinical presentation
Patients with osteomalacia may be asymptomatic or present with bone pain/tenderness and/or muscular weakness.
Pathology
Etiology
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vitamin D deficiency (most common)
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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)
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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 and other antiseizure medications)
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phosphate deficiency
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inadequate intake or absorption
antacids
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renal phosphate wasting
tumor-induced (oncogenic) osteomalacia, most commonly due to phosphaturic mesenchymal tumor
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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 5:
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diffuse demineralization: osteoporotic-like pattern
may show a characteristic smudgy "erased" or "fuzzy" type of demineralization 6
fuzzy/blurred appearance of the trabeculae 10
poor corticomedullary differentiation10
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articular manifestations (uncommon)
rheumatoid arthritis-like changes
osteogenic synovitis
ankylosing spondylitis-like changes