Mrs Benson, a 49-year-old teacher, came to the surgery for a review of her HRT three months ago. She also mentioned at this appointment that she has had worsening weakness, aching and incoordination in her arms and hands over the past few years. This had been especially bad this winter.
She had also been finding it more difficult to walk long distances and had noticed that her hair was becoming thinner, which she put down to going through the menopause last year. She has previously been fit and well with no past medical history of note.
She had some generalised weakness in most muscle groups of her arms and legs. Her reflexes were normal. There was some muscle wasting of her legs but this was only mild. She found it extremely difficult to stand from the squatting position.
In view of her history and clinical findings the GP decided to refer her to the local neurologist. The neurologist arranged for Mrs Benson to have multiple tests including an MRI scan of her lumbar spine, electromyography and nerve conduction studies. She had various blood tests including TFTs, fasting glucose and serum creatinine kinase. She also had an echocardiogram and an ECG.
When she was reviewed with the results of her tests she informed the GP that her eyelids were now becoming more drooping. She was also finding that her words are becoming mumbled, especially when tired in the evening, and she had episodes of difficulty in swallowing.
The results of the tests confirmed that this patient had myotonic dystrophy. This is an autosomal dominant inherited disorder in which the muscles contract but have decreasing power to relax. It affects about 1 in 8,000 people worldwide.
With this condition, the muscles become weak and waste away. Myotonic dystrophy can cause mental deficiency, hair loss and cataracts.
Onset of this rare disorder commonly occurs during young adulthood. But it can occur at any age and is extremely variable in degree of severity. The rate of deterioration is often slow, with little change over a long period of time.
The muscle weakness that occurs with myotonic dystrophy is variable and can range from mild to severe. It particularly involves the face and eyelids, jaw, neck, forearms and hands, lower legs and feet. It can affect speech and result in lack of facial expression.
Increased weakness in patients with myotonic dystrophy has been associated with hypothyroidism and certain cholesterol-lowering medications (such as statins). Some strength can return if these factors are eliminated.
Myotonia is a difficulty in relaxing a muscle after it has been contracted. For example, after gripping something it might be difficult to let go. This is worse in cold weather.
Cardiac problems may cause arrhythmias in patients with myotonic dystrophy, which may require treatment. They can affect adults, even those without symptoms, and regular ECGs are advised to detect problems at an early stage.
Less commonly, cardiomyopathy may occur. Patients therefore have a baseline echocardiography performed and regular ECG testing.
No specific treatment exists for the progressive weakness. A physiotherapist can help evaluate patients regarding the need for ankle-foot supports, or other assistive devices.
Support groups have been established for patients and families. Anxiety and depression are common in patients with myotonic dystrophy.
Rarely, myotonic dystrophy progresses to the point of wheelchair confinement. Weakness of the diaphragm and a susceptibility to aspiration increase the risk for aspiration pneumonia.
- Myotonic dystrophy can cause hair loss.
- There is no specific treatment for myotonic dystrophy.
- Hypothyroidism and statin use can worsen muscle weakness.
- Treatment is supportive.