What is the definition of Duane-Radial Ray Syndrome?
Duane-radial ray syndrome (DRRS) is a disorder that affects the eyes and causes abnormalities of bones in the arms and hands. This condition is characterized by a particular problem with eye movement called Duane anomaly (also known as Duane syndrome). Other features include bone abnormalities in the hands (malformed or absent thumbs, an extra thumb, or a thumb that looks like a finger) and partial or complete absence of bones in the forearm. Together, these hand and arm abnormalities are called radial ray malformations. DRRS is caused by mutations in the SALL4 gene and is inherited in an autosomal dominant manner. Treatment of DRRS may include surgery to correct Duane anomaly and radial ray malformations.
What are the alternative names for Duane-Radial Ray Syndrome?
- Okihiro syndrome
- DR syndrome
- Duane anomaly with radial abnormalities and deafness
- Acrorenoocular syndrome
What are the causes for Duane-Radial Ray Syndrome?
DRRS is caused by mutations in the SALL4 gene. The SALL4 gene is part of a group of genes called the SALL family. These genes provide instructions for making proteins that are involved in the formation of tissues and organs before birth. SALL proteins act as transcription factors, which means they attach (bind) to specific regions of DNA and help control the activity of particular genes. Mutations in the SALL4 gene prevent one copy of the gene in each cell from making any protein. It remains unclear how a reduction in the amount of SALL4 protein leads to Duane anomaly, radial ray malformations, and the other features of DRRS.
What are the symptoms for Duane-Radial Ray Syndrome?
DRRS is characterized by a particular problem with eye movement called Duane anomaly (also known as Duane syndrome). Duane anomaly results from the improper development of certain nerves that control eye movement. This condition limits outward eye movement (toward the ear), and in some cases may limit inward eye movement (toward the nose). As the eye moves inward, the eye opening becomes narrower and the eyeball may pull back (retract) into its socket. Duane syndrome may be unilateral (affecting only one eye) or bilateral (affecting both eyes).
Bone abnormalities in the hands include malformed or absent thumbs, an extra thumb, or a thumb that looks like a finger. Partial or complete absence of bones in the forearm is also common. Together, these hand and arm abnormalities are called radial ray malformations.
People with DRRS may have a variety of other signs and symptoms including unusually shaped ears, hearing loss, heart and kidney defects, a distinctive facial appearance, an inward- and downward-turning foot (a clubfoot), and fused spinal bones (vertebrae).
What are the current treatments for Duane-Radial Ray Syndrome?
The treatment of DRRS may vary and often requires a team of specialists. Severe strabismus associated with Duane syndrome and malformations of the hands and forearms may require eye surgery. Individuals with heart defects may also require corrective surgery. Hearing aids may be needed for those with hearing deficits. Growth hormone therapy may additionally be considered for individuals with short stature. Since kidney issues may develop, renal monitoring should also be considered.
Is Duane-Radial Ray Syndrome an inherited disorder?
DRRS is inherited in an autosomal dominant manner. This means that having a change (mutation) in only one copy of the responsible gene in each cell is enough to cause features of the condition.
In some cases, an affected person inherits the mutated gene from an affected parent. In other cases, the mutation occurs for the first time in a person with no family history of the condition. This is called a de novo mutation.
When a person with a mutation that causes an autosomal dominant condition has children, each child has a 50% (1 in 2) chance to inherit that mutation.