Osteogenesis Imperfecta Type II: A Fatal Disease

Presenter: H. Mannai (e-mail: [e-mail])

Introduction: Osteogenesis imperfecta (OI) describes a group of rare heritable disorders of connective tissue characterized by varying degrees of low bone mass and increased susceptibility to fractures. Most cases of OI are due to heritable defects in the synthesis or metabolism of type I collagen. OI occurs in all races and is the most common cause of primary osteoporosis with an incidence of between 1 in 10,000 and 1 in 20,000. The type II of OI is characterized by antenatal excessive bone fractures and is perinatally lethal.

Materials and Methods: We report two cases of osteogenesis imperfect type II. Clinical features and prognosis of OI are described referring to literature. First case: M.H; a male child born to a 22-year-old mother, gravida 1, para 1 from non-consanguineous marriage, by normal vaginal delivery at 38 weeks’ gestation. He has no family particular disease history. Antenatal ultrasonography performed at 22 weeks’ gestation (WG) disclosed a small-for-dates fetus with short and deformed upper and lower extremities, and multiple bone fractures with a strong suspicion of Lobstein disease. The baby had many limbs deformations with micromelia. After birth, the baby was immediately transferred to our intensive unit care where X-rays of the whole body were performed showing multiple displaced fractures with broad long bones, beading of the ribs and undermineralized skull. Of note, the sclerae were normal. The newborn died at day 2 of life. Second case: L N, a girl born to a 29-year-old mother, gravida 3, para 3, from second-degree consanguineous marriage. Previous pregnancies were normal. The first and second trimesters of this pregnancy were without complications. The first ultrasound performed at 25 WA had shown clubbed feet, arthrogryposis, and bilateral pyelectasis. The baby was born at 32 weeks’ gestation and 2 days. At delivery the neonate appeared edematous with a weight of 1,400 g. There was mid-face hypoplasia with low set ears and a short neck, as well as short, deformed upper and lower extremities. The initial Apgar score was 4 at 1 minutes and 6 at 5 minutes. Because of respiratory insufficiency, the child received mechanical ventilatory assistance in the delivery room. No response to the resuscitation was shown, no signs of sustained vitality appeared, and therefore respiratory support was discontinued after 10 hours. The infant expired shortly thereafter. The X-ray findings were typical of OI type II. Multiple rib fractures with callus were visible giving them a beaded appearance. Broad hypomineralized bones with multiple fractures could be evidences at all extremities resulting in “concertina” deformities of the femurs. Radiographs of the skull showed a brachycephalic deformity with hypertelorism and a thin, poorly ossified calvarium. X-rays of the chest revealed small hypoplastic lungs, but the thorax was not deformed (Figure 1).

Conclusion: Severe forms of OI are frequently diagnosed as a consequence of in utero ultrasound scanning. Though it is possible to confirm diagnosis using molecular genetic techniques, most cases receive a diagnostic confirmation only following birth or termination. In the future, techniques involving fetal DNA may enable an earlier diagnosis to be made in cases where there is known to be a risk of OI. The prognosis of the type II remains fatal in most cases which leads to the role of the medical interruption of pregnancy.

Keywords: osteogenesis imperfecta, newborn, rib fractures, heritable disorders

Fig. 1 Total Body Rx images of patient 2 affected by Osteogenesis imperfecta.