Osteogenesis imperfecta type VI

Osteogenesis imperfecta type VI is a moderate to severe form of osteogenesis imperfecta that affects the bones but is distinctive in the bone characteristics at a microscopic level (histology).  People with this condition have bones that are thin (osteopenia) and break easily beginning  after 6 months of age.  A defect in how the bone uses minerals to build and strengthen bone (mineralization) causes a distinct "fish-scale" pattern.  Unlike other types of osteogenesis imperfecta, the whites of the eyes (sclerae) and teeth do not appear to be affected.^[1][4]

Osteogenesis imperfecta type 6 has an autosomal recessive pattern of inheritance. Autosomal recessive inheritance means that two copies of the gene in each cell are altered. The parents of a child with an autosomal recessive disorder typically are not affected, but each carry one copy of the altered gene (they are referred to as carriers). When two carriers for an autosomal recessive condition have children, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier, and a 25% chance to not have the condition and not be a carrier. The children of an individual with an autosomal recessive type of OI are always carriers for a disease-causing mutation.^[5]

Genetic testing is available for individuals with osteogenesis imperfecta. The rate for detecting mutations in the genes that are responsible for OI varies depending on the type.^[5] Carrier testing may be available to relatives of affected individuals if the type of OI, disease-causing gene, and specific mutation in the affected individual are known.

Prenatal testing for at-risk pregnancies can be performed by analysis of collagen made by fetal cells obtained by chorionic villus sampling (CVS) at about ten to 12 weeks' gestation if an abnormality of collagen has been identified in cells from the affected individual. Analysis of collagen after an amniocentesis (usually performed at 15-20 weeks gestation) is not useful, because the cells obtained do not produce type I collagen. However, prenatal testing can be performed by analyzing the genes (molecular genetic testing) if the specific mutation has been identified in the affected relative.^[5]

GeneTests lists the names of laboratories that are performing genetic testing for different types of osteogenesis imperfecta. To view the contact information for the clinical laboratories conducting testing, click here and click on "Testing" next to the type of OI in which you are interested. Please note that most of the laboratories listed through GeneTests do not accept direct contact from patients and their families; therefore, if you are interested in learning more, you will need to work with a health care provider or genetics professional. Genetics professionals, such as genetic counselors, can also explain the inheritance of OI in detail including information about genetic risks to specific family members.

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.