This is a 26-year-old, primigravida, referred to our unit at 17 weeks’ gestation for a routine scan. This fetus has several findings including:

• hypomineralization of the skull (but the skull did not appear "compressible")
• hypomineralization of long bones
• market shortening of all four limbs
• short ribs
• angulated fibula-tibia
• normal spine mineralization

The rib shortening is pathognomonic of the lethal skeletal dysplasias due to hypoplasia of the lungs. The others findings were very suggestive of osteogenesis imperfect type II.

The parents were counseled and they opted for the interruption of the pregnancy. The postnatal x-ray and photographs confirmed the prenatal findings. Genetic material was sent to assess the exact type of dysplasia and the recurrence risk.

During the visit to the genetic counselor, the family history of the couple was reviewed and it was negative for osteogenesis imperfecta, multiple bone fractures, multiple miscarriages, mental retardation or any other genetic condition. The biochemical testing performed in skin fibroblasts of their baby confirmed the diagnosis of osteogenesis imperfect type II (OI type 2). The biochemical testing performed in cultured skin fibroblasts of their baby (which analyzed the structure and quantity of type I collagen) is able to detect abnormalities in 98% of the individuals with OI type 2. However, molecular genetic testing that look for a specific mutation in the collagen gene was not performed.

The majoirty of the fetus with OI (type 2) have a de novo mutation. The recurrence risk for the next pregnancy is about 2-5% due to the possibility of gonadal mosaicism in the parents.

Note the hypomineralization of the skull

Note the short ribs and the bell-shaped chest

The market shortening of all four limbs and the "transparency" of the bones whose both cortical are seen

Postnatal view. Note the "soft" skull and the shortening of all four limbs

Postnatal radiography confirming the shortening and the hypomineralization of the long bones