What Is Oculopharyngeal Muscular Dystrophy?

Female doctor in face mask examining male patient’s eyelids

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Oculopharyngeal muscular dystrophy (OPMD) is a rare genetic condition that affects people of any sex. OPMD causes slowly progressive weakness in the muscles of the upper eyelids and throat. Onset typically occurs between the ages of 40 and 60.

OPMD is a type of muscular dystrophy (MD), an inherited disease that causes progressive weakness and degeneration of the skeletal muscles. Age of onset, severity of symptoms, muscles affected, and inheritance pattern vary between the over 30 types of MD.

In oculopharyngeal muscular dystrophy, a genetic defect causes the production of a nonfunctional protein, which clumps in the muscle cells. This clumping mainly affects the muscles of the upper eyelids and throat, causing a variety of symptoms. OPMD can be inherited from one or both parents.

Female doctor in face mask examining male patient’s eyelids

Portra / Getty Images

Types of Oculopharyngeal Muscular Dystrophy

There are two types of OPMD—autosomal dominant and autosomal recessive. Each type is distinguished by the pattern of inheritance. Because the defective gene is not on a sex chromosome, the condition is seen in people of any sex.

Most cases of OPMD are autosomal dominant. In the autosomal dominant pattern, it only takes a gene inherited from one parent to produce the condition. Autosomal recessive types of OPMD require the defective gene to be inherited from both parents for the condition to occur.

Those with the autosomal recessive type of OPMD tend to have more severe symptoms and an earlier onset of the disease than those with the autosomal dominant type.

Oculopharyngeal Muscular Dystrophy Symptoms

Although the affected gene is present at birth, symptoms of OPMD do not usually appear until adulthood. These symptoms are caused by the progressive weakening of the muscles around the eyelids and in the throat.

In some cases, the pelvic and shoulder areas can be affected as well, including the muscles of the upper arms and legs.

The most common symptoms of OPMD are:

Drooping of the eyelid (ptosis) can cause difficulty with sight, forcing you to tilt your head back in order to see. Over time, more muscles around the eye may weaken, potentially limiting eye movement. This is rarely a complete limitation. Some people may experience double vision.

If you experience difficulty swallowing, you may feel as if you have food stuck in your throat. Severe difficulties in swallowing can lead to food or liquid in the lungs, which can cause infection, inflammation, or aspiration pneumonia.

As the disease progresses, other symptoms are possible. These include but are not limited to:

  • Weakness/atrophy of the muscles of the upper legs, shoulders, pelvis
  • Difficulty kneeling, climbing stairs, walking, or squatting
  • Weakness/atrophy of the tongue
  • Difficulty speaking
  • Weakness of other facial muscles

Causes

OPMD is caused by a mutation in the polyadenylate binding protein nuclear 1 (PABPN1) gene. This gene normally carries instructions to provide the polyadenylate binding protein to muscle cells. It was discovered in 1998.

The defective gene is suspected to add extra amino acids in the PABPN1 protein which then causes them to clump together. This interferes with muscle cell function, causing symptoms like eye drooping and difficulty swallowing.

Diagnosis

Diagnosing OPMD can be challenging due to its overlap of symptoms and features of several other neuromuscular diseases, particularly myasthenia gravis. Often, OPMD is misdiagnosed or underdiagnosed because of this overlap.

To be certain of the diagnosis, your doctor will take a thorough history and conduct a full clinical evaluation. They will look for key symptoms of OPMD, such as droopy eyelids, difficulty swallowing, and difficulty speaking.

If your doctor suspects you have OPMD, they will confirm it with a blood test. Commercially available, this will test for the genetic abnormality in the PABPN1 gene. Most often, this will be enough to confirm the diagnosis.

However, if the blood test results do not show the genetic mutation in the PABPN1 gene and your doctor still suspects you have OPMD, they may order a muscle biopsy. The muscle biopsy can help confirm or rule out a diagnosis of OPMD.

The muscle biopsy looks for abnormal PABPN1 proteins in the cells. These abnormal proteins form clumps within the cells. If they are detected, an OPMD diagnosis can be confirmed as these are specific to the disease.

With the muscle biopsy, your doctor may also look for other common findings in OPMD that are less specific but can help with diagnosis. These include variation in the diameter and appearance of muscle fibers and ragged red fibers.

Treatment

While there is no cure for OPMD, there are treatments that can help you manage specific symptoms and maintain quality of life.

Droopy Eyelids

Plastic surgery on the eyelids (blepharoptosis repair) can help you see by raising your eyelids. However, since the eyelids are weak, you may not be able to fully close your eyelids after surgery.

Difficulty Swallowing

For less severe difficulty swallowing, therapy and diet changes can help. Therapy can teach you ways to maneuver around the weak muscles, such as holding the head in a different position when eating.

Diet changes can include using commercial thickeners to give liquids a consistency that is easier to manage and help you avoid aspiration. In the case where difficulty swallowing is severe, you may need a nonsurgical procedure called throat stretching.

For even more severe cases, a surgical procedure known as cricopharyngeal myotomy may be necessary. In this procedure, the cricopharyngeal muscle in the throat is cut so that it remains relaxed while swallowing, to allow the passage of food or liquid.

For advanced cases, tube feeding may be necessary.

Limb Weakness

If you have trouble picking up your feet while walking due to weakness, assistive devices can help you move around. A cane, walker, or leg braces may be prescribed.

Occupational therapy can help address weakness that limits mobility in your upper arms and shoulders with adaptive techniques.

Prognosis

With OPMD, you can expect a normal lifespan. Since OPMD is a progressive disease, however, you can expect symptoms to change over time.

The major determining factor in the quality of life with OPMD is the severity of the difficulty swallowing. This can lead to poor nutrition and sometimes life-threatening respiratory infections.

With typical OPMD, most people begin to experience weakness in their arms or legs about seven years after the onset of droopy eyelids or difficulty swallowing. In severe OPMD, some people may eventually need a wheelchair.

Coping

Learning to cope with any diagnosis takes time. Seeking out proper medical care and emotional support should be a priority.

You may also find that connecting with others who experience the same symptoms can help you feel less alone. For resources on connecting with others, contact the Muscular Dystrophy Association.

A Word From Verywell

If you suspect you have OPMD, talk to your doctor. As discussed, OPMD can mimic other neuromuscular diseases. To receive proper treatment, you need the correct diagnosis.

Don’t be afraid to seek a second opinion if necessary, and know that any diagnosis comes with challenges, but with proper care, they can be managed.

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Article Sources
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