Fetal abnormalities » Skeleton
- 1 in 15,000 births.
- The most common are types I and IV.
- Spectrum of the defects characterized by fragile bones.
- There are at least eight recognized forms of osteogenesis imperfecta, designated type I through type VIII with overlapping characteristic features. Type I is the mildest form and type II is the most severe; signs and symptoms of the other types fall somewhere between these two extremes.
- Most cases that present prenatally are types II and III:
- Type I: fragile bones, blue sclerae and progressive deafness. Ultrasonography in the second and third trimesters may demonstrate fractures of long bones.
- Type II: short limbs and ribs with multiple fractures, hypomineralization of the skull.
- Type III: multiple fractures, usually present at birth, resulting in scoliosis and very short stature.
- Detailed ultrasound examination.
- Detailed family history and consultation with geneticist.
- Osteogenesis imperfecta is caused by mutations in the COL1A1, COL1A2, CRTAP, and P3H1 genes.
- Prenatal diagnosis of types II, III, and IV can be made by invasive testing.
- Follow-up should be standard.
- Standard obstetric care and delivery in a tertiary center.
- Type I: normal life expectancy.
- Type II: lethal.
- Type III: motor disability (kyphoscoliosis, fractures), hearing loss in adulthood.
- De novo Most cases of osteogenesis imperfecta have an autosomal dominant pattern of inheritance, but most infants with more severe forms of the condition (types II and III) are caused by new mutations.