Oculopharyngeal muscular dystrophy (OPMD)

Oculopharyngeal muscular dystrophy (OPMD) refers to a genetic condition that causes muscle weakness in a characteristic pattern.

It is useful to explain the words that make up OPMD:

• oculo refers to the fact that the eye muscles (specifically the eyelids) are affected, causing eyelid drooping – also called ‘ptosis’
• pharyngeal refers to the fact that the throat muscles, in particular those related to swallowing, are affected. Difficulty in swallowing is called dysphagia
• muscular dystrophy is a term which usually means the condition is genetic, and causes progressive muscle wasting and weakness, both of which are true in OPMD.

People with OPMD do not usually develop symptoms until after the age of 40, with an average age of onset of around 50.

The first sign of the condition is either ptosis, or dysphagia (difficulty swallowing). Very slowly, over many years, these problems worsen.

The increasing ptosis may lead to the eyelid covering the pupil and so obstructing vision. In an effort to compensate for this, the forehead muscles become overactive, trying to help lift up the eyelids. People with OPMD often adopt a rather characteristic posture with the head tilted backwards to see clearly. However, the eye itself is not affected, and even when the condition is advanced, people with OPMD have normal vision if the eyelids are raised.

Dysphagia, which initially mainly affects swallowing solid and dry foods, progresses slowly. Eventually even swallowing fluids, including saliva, may become a problem. If dysphagia is severe, there is a danger of aspiration (food, drink or saliva ‘going down the wrong way’ into the chest rather than stomach), which increases the risk of a chest infection (aspiration pneumonia).

Many years after the onset of the condition, people with OPMD may become aware of limb weakness, often first around the shoulders and later around the hips. This is often relatively mild but can progress to be more severe and disabling, many years after the first onset of symptoms. Life-expectancy, with modern management of the condition, is close to normal.

In almost all cases, the condition is inherited as an autosomal dominant disorder, which means that each child of an affected individual has a 50 percent risk of inheriting the condition.

If someone in a family with known OPMD develops likely symptoms, then a diagnostic genetic test will often be advised.

Image showing one unaffected parent and one affected parent have a 50% chance of having a child who inherits the condition
Sometimes, people with a parent with OPMD wish to know whether they are likely to develop the condition. They may wish to consider a predictive test (i.e. prior to symptoms). After suitable discussion/counselling of the advantages and disadvantages of having this knowledge, a genetic test may be offered. In this situation, however, when a family member has inherited the mutated gene, it remains impossible to predict precisely when they will develop symptoms.

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