Osteogenesis imperfecta

• this is a disease of collagen molecules covering a spectrum of severity; this variation is caused by differences in the particular defect in collagen synthesis

  • collagen is a triple helix containing pro-α1 and α2 collagen

  • genetic defects include a single substitution of glycine or a point mutation or deletion

• in any case, the collagen is not normal, and depending on what type of alteration you are dealing with, you get different types of osteogenesis imperfecta

• there used to be four types of osteogenesis imperfecta; clinical manifestations range from short stature and propensity to fractures all the way to a lethal disease at the time of birth

  • type I not severe

  • type II lethal form

  • type III in between types I and II, but more progressive

  • type IV is between types I and III

• you can imagine a list of affected structures in osteogenesis perfecta

  • skeleton

  • ligaments

  • sclera

  • teeth

micrograph: normal osteogenesis

• there is a very regular, well-orchestrated progression of chondrocytes, spongiosa

• various imperfections in this pathway can lead to osteogenesis imperfecta

gross specimens

• type III osteogenesis imperfecta: progressive type. deformities, fractures, scoliosis, small pelvic bone

• dentinogenesis imperfecta, characteristic of some types of osteogenesis imperfecta: abnormal dentin synthesis, which eventually leads to abnormal tooth formation

• blue sclera

• fracture and deformity of the humerus, and the overall strange appearance of the child

• scoliosis leading to fracture and compression of the vertebral column; indeed, many patients are in severe pain. these are termed fish-mouth vertebra

• upper tibia: growth plate in child is disrupted by bleeding; X-ray reveals an irregular and markedly-displaced growth plate. you can see areas of irregular calcification in the cartilage

Category: Pathology Notes