| Osteogenesis Imperfecta Type II |
OI Type II is the most severe form. At birth, infants with OI Type II have very short limbs, small chests, and soft skulls. Their legs are often in a frog-leg position. The radiologic features are characteristic and include absent or limited calvarial mineralization; flat vertebral bodies; very short, telescoped, broad femurs; beaded and often broad short ribs; and evidence of malformation of the long bones. Intrauterine fractures will be evident in the skull, long bones, or vertebrae. The sclerae are usually very dark blue or gray and their lungs are underdeveloped. Infants with OI Type II have low birth weights and respiratory and swallowing problems are common. Macrocephaly may be present but microcephaly is rarely present. Infants with OI Type II usually die within weeks of delivery. A few may survive longer. Cause of death is usually respiratory and cardiac complications. OI Type II results from a new dominant mutation in a type 1 collagen gene or parental mosaicism. Similar extremely severe types of OI, Types VII and VIII, can be caused by recessive mutations to other genes. Genetic counseling is recommended for parents of a child with OI Type II before any future pregnancies. Significant care issues that arise with OI Type II include obtaining an accurate diagnosis, getting genetic counseling, the family’s need for emotional support, and management of respiratory and cardiac impairments. Infants with OI Type II who can breathe without a respirator and those with severe OI Type III may be candidates for off-label treatment with bisphosphonates. At this time, pamidronate (©Aredia) is the only bisphosphonate that has been studied in infants who have OI. Treatment research is ongoing.
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