Babies with Type I OI may or may not be born with fractures. A baby may have other outward signs of OI, such as blue-tinted sclera or loose joints, but these signs may go unnoticed in a family with no history or knowledge of OI. Furthermore, blue sclera can be seen even in infants without OI until about 18 months of age.
A child with Type I OI may sustain his or her first fracture during some ordinary activity, such as when a caregiver pulls on the ankles while changing a diaper, a doctor does a physical exam, or a toddler falls while learning to walk. Other children with OI may not experience fractures until the school years, when they begin participating in physical education, sports, and recreational activities.
The occurrence of a fracture after little or no injury is often the first clue that a child may have OI. To diagnose the disorder, a doctor can look for other clinical features of OI, including standard x rays, which may show evidence of “thin bones.” The doctor also can obtain a family history to determine if other family members have had repeated fractures or other OI symptoms.
Diagnosis of OI is based primarily on clinical signs. Collagen testing of a skin biopsy sample or DNA testing of a blood sample can help confirm a diagnosis of OI in most situations. However, a negative OI test does not necessarily rule out an OI diagnosis. Some individuals test negative for OI despite having the disorder. In some especially rare forms of OI, there is no collagen defect.
Families in which one parent has OI may be able to arrange for prenatal testing through chorionic villus sampling or amniocentesis. In most cases of Type I OI, this type of prenatal diagnosis requires knowledge of the affected parent's genetic mutation. Ultrasound may not detect Type I OI in a fetus, because the child is unlikely to have fractures or bone deformity before birth. When prenatal diagnosis is impossible or not desired, a sample of blood from the child's umbilical cord can be taken at birth and sent for DNA analysis.
When a parent has OI, it is recommended that the newborn be tested and examined as soon as possible by a doctor who is knowledgeable about OI. The information will help parents make decisions about their baby's care and help protect the family from unwarranted child abuse allegations.