Marcus Gunn syndrome: what is it, causes, symptoms, treatment, prognosis

What is Marcus Gunn Syndrome?

Marcus Gunn SyndromeIs a rare genetic disorder characterized by the movement of the upper eyelid with a rapid upward "wink" with each movement of the jaw. This winking phenomenon can be caused by opening the mouth, pushing the jaw to the side, protruding the jaw, chewing, smiling, or sucking. It is usually present at birth and can occur with other visual impairments (eg, strabismus) or vision problems. Although the disorder usually affects one eye, in rare cases it can affect both eyes. The exact reason is not known. Marcus Gunn syndrome is usually sporadic, but familial cases have been reported. Treatment is not always necessary, but may include surgery in more severe cases.

The syndrome was described in 1883. by London ophthalmologist Markus Gunn at a 15-year-old girl and bears his name.

Signs and symptoms

In most patients with Marcus Gunn syndrome, the upper eyelid of one eye (unilateral) drops (i.e. blepharoptosis occurs). The main symptom of this disorder is rapid and involuntary upward movement of the affected eyelid after almost any movement of the mandible. As a result, this eye appears to open even wider. This appears for the first time shortly after birth, especially during feeding and sucking. These actions cause the eyelid to move up and down. Several cases of the disorder have been seen in adults.

People with the Marcus Gunn phenomenon may experience visual impairments such as uneven direction of the eye pupils (strabismus), slight deterioration of vision in one eye compared to the other (difference in refractive power of the eyes [anisometropia] and other problems (eg superior rectus palsy).

In some cases, symptoms may be triggered by lip movement, whistling, smiling, clenching the teeth, chewing, puffing out the cheeks, or swallowing.

Causes

The exact cause of Marcus Gunn syndrome is unknown. For unknown reasons, there is a poor connection between stimulating nerves and moving muscles, eyelids and jaws. Some clinical researchers believe that about half of the cases of the Marcus Gunn phenomenon are genetically determined. The location and nature of the gene (s) responsible for this disorder is unknown, but family studies indicate that it is transmitted as an autosomal dominant trait.

Chromosomes, which are present in the nucleus of human cells, carry the genetic information of each person. The cells of the human body usually have 46 chromosomes. Pairs of human chromosomes are numbered 1 through 22, and the sex chromosomes are labeled X and Y. Men have one X and one Y chromosome, while women have two X chromosomes. Each chromosome has a short arm, denoted p, and a long arm, denoted q. Chromosomes are further subdivided into multiple bands, which are numbered. For example, chromosome 11p13 is in lane 13 on the short arm of chromosome 11. The numbered stripes indicate the location of the thousands of genes present on each chromosome.

Genetic diseases are defined by a combination of genes for a specific trait, which are found on chromosomes received from the father and mother.

Dominant genetic disorders occur when only one copy of an abnormal gene is needed for a disease to appear. The abnormal gene can be inherited from either parent, or it can be the result of a new mutation (gene change) in the affected person. The risk of passing the abnormal gene from the affected parent to the offspring is 50% with every pregnancy, regardless of the sex of the child.

Affected populations

Marcus Gunn Syndrome is a rare genetic disorder present at birth. The disorder affects men and women equally. Only about 300 cases of the disease have been reported in the medical literature.

Symptomatic disorders

Marcus Gunn syndrome can occur in conjunction with certain other visual impairments, such as Duane's syndrome or retinitis pigmentosa.

Some types of facial nerve injuries can cause symptoms similar to Marcus Gunn's syndrome.

• Marine Amata Syndrome similar to the Marcus Gunn phenomenon, except that the eye closes rather than opening wider when the jaw opens or moves. This disorder is also referred to as the “reverse Marcus Gunn phenomenon”.
• Orofacial digital syndrome is a rare genetic disorder. In patients with type III of this syndrome (Sugarman's syndrome), when the lower jaw moves, the eyelid involuntarily and quickly rises, as a result of which the eye opens wider. Patients have more teeth than usual. Other major symptoms may include disorders involving the nervous and muscular (neuromuscular) systems, congenital malformations (present at birth) such as cleft palate and cleft lip, other deformities of the face, malformations of the arms and legs, shortened limbs and various degrees of mental retardation.
• Lipo-palpebral synkinesis - a rare disease characterized by the rise of the upper eyelid of one eye when a person smiles.

Diagnostics

The diagnosis is straightforward and is often made by one or both parents who become aware of the main symptom while feeding.

Standard treatments

Treatment for Marcus Gunn syndrome is usually not required as the condition becomes less noticeable with age. Genetic counseling can be beneficial for patients and their families. Other vision problems, such as squint, amblyopia and so on. can be corrected with glasses, surgery and / or drugs.

Surgical correction of a drooping eyelid or wink is only recommended if the patient (or parents) agree on which of the symptoms is more cosmetically undesirable. Surgical procedures are available at varying intensities of drooping of the eyelids.

Forecast

The prognosis for the Marcus Gunn phenomenon is favorable. Older individuals often report that palpebromandibular synkinesis diminishes over time. However, this is not confirmed by objective research data. Probably, older people pay less attention to synkinesis or have learned to mask them. However, with severe ptosis and synkinesis, when combined with strabismus and amblyopia, surgical treatment is indicated.

Lilia Khabibulina/ article author