U01.01.034 Osteogenesis imperfecta

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Learning Objectives

  • Identify the genetic basis and collagen type involved in OI.
  • Master the BITE mnemonic for clinical manifestations.
  • Distinguish OI from child abuse in a clinical setting.
  • Understand the role of Bisphosphonates in treatment.

1. Pathophysiology

Osteogenesis Imperfecta (Brittle Bone Disease) is a genetic disorder of connective tissue. The most common form is Autosomal Dominant.

  • Genetic Defect: Mutations usually occur in the COL1A1 and COL1A2 genes.
  • Mechanism: Leads to decreased (\downarrow) production of otherwise normal Type I Collagen. The defect specifically impacts triple helix formation during synthesis.

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2. Clinical Manifestations: The BITE Mnemonic

Because Type I collagen is found in bone, skin, teeth, and eyes, the symptoms are widespread.

Mnemonic Clinical Finding Mechanism
Bones Multiple Fractures Minimal trauma (e.g., during birth) leads to fractures and deformities.
I (Eye) Blue Sclerae Thin, translucent collagen allows the underlying choroidal veins to show through.
Teeth Dental Imperfections Dentinogenesis imperfecta: opalescent teeth that wear easily due to a lack of dentin.
Ear Hearing Loss Related to abnormalities of the ossicles (the tiny bones of the middle ear).

3. Clinical High-Yields & Treatment

  • Diagnostic Dilemma: Because of the frequent fractures, OI may be confused with child abuse. A thorough physical exam looking for blue sclerae and dental issues is crucial.
  • Pharmacology: Treatment often involves Bisphosphonates (e.g., Alendronate) to increase bone mineral density and decrease the risk of fractures.

 

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