Duane syndrome

The following list includes the most common signs and symptoms in people with Duane syndrome. These features may be different from person to person. Some people may have more symptoms than others and they can range from mild to severe. This list does not include every symptom that has been described in the condition.

Symptoms of Duane syndrome may include:^[1][2] 

• Two eyes that don't line up in the same direction (strabismus)
• Limited ability to move the eye from side to side
• Retracted eyeball (pulled back into the socket)
• Narrow eye opening (narrow palpebral fissures)
• Lazy eye (amblyopia)

Duane syndrome is present at birth and infants may have only a limited ability to move the affected eye outward and/or inward. Some people with Duane syndrome are at risk to develop lazy eye and have decreased vision in that eye. People with Duane syndrome may also have unusual head movements. Generally, with treatment, eye movement can be corrected.^[2][4] 

Duane syndrome has 3 types which vary depending on which type of eye movement is most restricted. In Duane syndrome type 1, eye movement outward is limited. This is the most common type of Duane syndrome. In Duane syndrome type 2, eye movement inward is limited. In Duane syndrome type 3, both outward and inward eye movement are limited.^[1][2]

In about 30% of cases, Duane syndrome occurs with other abnormalities or as part of a genetic syndrome.^[1]

Duane syndrome is caused by an abnormality in the early development of the cranial nerve involved in eye movement. The exact cause for this is unknown.^[4]

Duane syndrome usually occurs in a family for the first time, without any previous family history. In some cases, Duane syndrome is inherited from an affected parent. In these cases, Duane syndrome may occur when the CHN1, MAFB, or SALL4 gene is not working correctly. DNA changes known as pathogenic variants are responsible for making genes work incorrectly or sometimes, not at all.^[1][3]

Duane syndrome associated with MAFB gene variants typically occurs with hearing loss. Duane syndrome associated with SALL4 gene variants typically causes Duane-radial ray syndrome (DRRS), a condition which includes Duane syndrome and upper limb abnormalities.^[1][3]

In most cases, Duane syndrome is not inherited. The majority of cases of Duane syndrome occur in individuals with no history of the condition in the family.^[1][2] 

About 10% of people with Duane syndrome have other family members with Duane syndrome. In these families, Duane syndrome is inherited in an autosomal dominant pattern.^[1][2] All individuals inherit two copies of each gene. Autosomal means the gene is found on one of the numbered chromosomes found in both sexes. Dominant means that only one altered copy of a gene is necessary to have the condition. The variant can be inherited from either parent. Sometimes an autosomal dominant condition occurs because of a new genetic variant (de novo) and there is no history of this condition in the family.
 
Each child of an individual with an autosomal dominant condition has a 50% or 1 in 2 chance of inheriting the variant and the condition. Typically, children who inherit a dominant variant will have the condition, but they may be more or less severely affected than their parent.

Sometimes a person may have a gene variant for an autosomal dominant condition and show no signs or symptoms of the condition. This is called reduced penetrance, and has been reported in families with Duane syndrome.

Duane syndrome is diagnosed based on the symptoms, eye exam, and imaging studies. Genetic testing may be helpful if there are multiple family members with Duane syndrome.^[1][3]

The treatment of Duane syndrome is focused on managing the symptoms. Options include corrective eye glasses or contacts, and eye surgery. Some of the indications for surgery include abnormal head positioning, an eyeball that is pushed back, or very narrow opening for the eye.^[3][4]

Specialists involved in the care of someone with Duane syndrome include:

• Ophthalmologist
• Ophthalmic surgeon
• Medical geneticist

It has been estimated that approximately 1 in 1000 and 1 in 10,000 people worldwide have Duane syndrome. Duane syndrome is found in 1-5% of all cases that involve conditions where both eyes do not line up in the same direction (strabismus). Females are more likely to be affected than males. Most cases involve only one eye.^[1][3][4]