Osteogenesis imperfecta type VI

Alternate names

OI type 6; OI6; OI type VI; Osteogenesis imperfecta type; SERPINFI- related osteogenesis imperfecta

Definition

Osteogenesis imperfecta type 6 is a form of osteogenesis imperfecta which results in weakened bones that breaks easily. When viewed under a microscope, bone tissue has a distinct "fish-scale" pattern.

Cause

Osteogenesis imperfecta type 6 may be caused by mutations in the SERPINF1 gene.

Inheritance

Autosomal recessive inheritance, a 25% chance

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.

Signs and symptoms

• 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.

Diagnosis

• Diagnosed by bone biopsy or genetic studies.
• 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.
• 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.

Treatment

There is no cure for OI. The goal of treatment, depending on the type of OI, is to prevent or control symptoms, increase bone mass and muscle strength, and maximize a person’s ability to be independent. These treatments include:

Physical or Occupational Therapy People with OI may benefit from physical or occupational therapy, which can help the person:

• Build muscle strength; improve joint movement, mobility, and gross motor skills; and prevent broken bones.
• Learn how to avoid injuries.
• Safely perform activities of daily living.
• Recover from broken bones.
• Therapists and doctors also may recommend swimming to condition and build strength.

Medicines Although there are no medicines approved by the U.S. Food and Drug Administration to treat OI, your doctor may recommend a therapy approved for a related condition. Your doctor may prescribe:

• Bone strengthening medicines approved to treat other bone diseases can help slow bone loss and reduce the frequency and seriousness of broken bones.
• Pain medicines to treat pain caused by broken bones and chronic bone pain.
• In addition, some medicines are currently being studied to help prevent the complications of or to treat OI in adults and children. Talk to your primary care provider or your child’s pediatrician about the using these medicines or participating in studies.

Bone Care

• An orthopaedic specialist can treat broken bones with a cast, splint, or brace. Sometimes people need surgery to repair a broken bone.
• In addition, doctors perform surgery to support or correct bones that are curved or bowed, including the spine.
• Many children with OI have rodding surgery, in which a metal rod is placed into a bone. Rodding surgery is performed to support the bone and prevent the bone from breaking.
• Some of these rods are “telescoping” and can be adjusted to lengthen as a child with OI grows.

Mobility Aids Using a mobility aid may help people safely perform daily activities and reduce injuries. These aids include:

• Walkers.
• Canes and crutches.
• Braces or prosthetics.
• Wheelchairs.
• Oral and Dental Care

Some people with OI have:

• Teeth that easily chip or break.
• Changes in tooth color and shape.
• Tooth decay.
• Small jaw size.
• Incorrect position of teeth.

Regular dental check-ups and care are important to prevent dental symptoms and improve bite, alignment and appearance of teeth. In addition, some people need to see:

• Oral-maxillofacial surgeon, who specializes in oral and jaw surgery.
• Orthodontist, who treats tooth alignment and jaw position.

Hearing Doctors recommend hearing testing beginning in childhood, with regular testing throughout the person’s life. It’s important to see an audiologist who specializes in caring for people with OI. Treatment can include:

• Hearing aids, small electronic devices worn outside the ear that make sound louder.
• Cochlear implants, small electronic devices that have two pieces, one outside behind the ear and another under the skin.
• Surgery called stapedectomy, when a surgeon places a prosthetic or artificial device into the middle ear, allowing sound waves to reach the inner ear.

NIH genetic and rare disease info

• NIH info on Osteogenesis imperfecta type VI

Osteogenesis imperfecta type VI is a rare disease.

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