2009-10-10-10 Osteogenesis imperfecta, type II © Binodini www.thefetus.net/
Osteogenesis imperfecta, type II
A 22-year-old woman of a non-consanguineous marriage was referred to our department for a 2nd opinion scan due to a finding of short fetal limbs. This was her second pregnancy, and the first one ended as a miscarriage at 3rd month of the pregnancy. Her family history was not contributive and she did not take any drugs during the pregnancy.
Our ultrasound revealed a 26-27 weeks old singleton intrauterine pregnancy with several abnormal findings:
Head: The skull was abnormally echopenic and compressible due to poor bone mineralization;
Thorax: The thorax appeared narrow and bell-shaped with collapsed ribs of beaded appearance due to intra-uterine fractures; both lungs appeared hypoplastic with no evidence of pleural or pericardial effusion, and the thoracic circumference was below 2.5th percentile of the gestational age;
Limbs: All fetal long bones were extremely short (below 2 SD) and appeared bent and irregular (due to intrauterine fractures) and poorly ossified.
The findings were suggestive of a lethal skeletal dysplasia, most probably of the osteogenesis imperfecta type II (in our differential diagnostic, hypophosphatasia and achondrogenesis type I also came into consideration).
As the presumptive outcome of the pregnancy was unfavorable, the couple opted for the termination of the pregnancy.
At postnatal examination the fetus weighing 850 grams, with a large membranous skull and short limbs. The lower limbs were bent and shorter than the upper limbs. The hands and feet were normal, the face showed protruding tongue and partially opened eyes, and the abdomen was bulging. The back and spine looked normally.
X-ray examination of the fetal skeleton showed poor mineralization of the fetal skull with preserved mineralization of the spine. The ribs were short and of beaded appearance due to multiple the intrauterine fractures. The femurs appeared bent and fractured with poor mineralization. The tibia and fibula were also short and bent. The upper limb bones also appeared short, fractured and poorly mineralized. Overall the skeleton was poorly mineralized with multiple fractures.
The final diagnosis was the osteogenesis imperfecta, type II. The osteogenesis imperfecta type II represents a “de novo" dominant mutation and its recurrence risk about 2-5 %.
Images 1, 2, 3, and 4: The images show transverse scans of the fetal head with increased echogenicity of the intracranial structures. The skull is easily compressible by the ultrasonographic probe - arrows on the image 4).
Video 1: The video demonstrates the easy compressibility of the fetal head.
Images 5, 6: The images demonstrate narrow fetal thorax with short, irregular ribs.
Images 7, 8: The images show short, bent femur of the fetus. Note that the both cortical layers of the femur are well recognizable (arrows on the image 8).
Image 9: The image shows short, bent bones of the upper extremity of the fetus.
Images 10, 11: 3D images; the image 10 shows abnormal, beaded ribs. The image 11 shows short upper limbs of the fetus.
Images 12, 13: 3D images; the image 12 shows short upper limb of the fetus; the image 13 shows the fetal profile and face with partially opened eyes (not contributive to the diagnosis).
Images 14, 15: The images show appearance of the aborted fetus.
Images 16, 17, 18, and 19: X-ray images demonstrating the overall hypomineralized skeleton with short, bent, irregular long bones, narrow bell-shaped thorax with abnormal ribs and extremely hypomineralized skull.