Osteogenesis Imperfecta

Basics

Description

  • Inherited abnormality of procollagen amino acid sequence leading to abnormal type I collagen
  • “Brittle bone disease”
  • Bone hypomineralization and incomplete ossification result in brittle bones
  • Incidence is 1/10,000 to 1/20,000 live births
  • Abnormal collagen affects all connective tissue to varying degrees
  • Time course is variable:
    • Most cases involve fractures starting when children begin standing, continuing through teenage years, with decreased incidence as adults

Etiology

  • Procollagen defects result in abnormalities of bone and connective tissue matrix
  • Defects in different sites on procollagen protein chain result in more severe forms
  • Defects are inherited: Autosomal recessive (typically more severe), autosomal dominant (more common but can be less severe), or X-linked (males > females)
  • Lethal cases involve sporadic or new mutations
  • Ehlers–Danlos syndrome involves mutations of the same procollagen protein in different locations

Pediatric Considerations

  • Milder cases involve pathologic fractures during childhood, but severe forms can occur in utero
  • Multiple fractures often initiate evaluation for nonaccidental trauma, but the possibility of pathologic fractures should also be considered

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