Myotonic Dystrophy - Diagnosis

Diagnosis

The diagnosis of DM1 and DM2 can be difficult due to the large number of neuromuscular disorders, most of which are very rare. More than 40 neuromuscular disorders exist with close to 100 variants.

As a result, patients with multiple symptoms that may be explained by a complex disorder such as DM1 or DM2 will generally be referred by their primary care physician to a neurologist for diagnosis. Depending on the presentation of symptoms, patients may be referred to a number of medical specialists including cardiologists, ophthalmologists, endocrinologists, and rheumatologists. In addition, the clinical presentation is obscured by the degree of severity or the presence of unusual phenotypes.

It is common that the clinical presentation for both DM1 and DM2 patients does not conform to the perceptions of these diseases held by many neurologists. Clinicians who are less familiar with the myotonic dystrophies in their day to day practice may expect patients with both forms to present with the more severe classic symptoms of DM1. As a result, patients may remain undiagnosed or be misdiagnosed. A useful clinical clue for diagnosis is the failure of spontaneous letting go of the hands following strong handshakes due to myotonia (delayed relaxation of muscles after contraction) which accompanies muscle weakness.

Even though there is presently no cure for DM and management is currently symptom based, a precise diagnosis is still necessary because of multiple other problems that may develop over time (e.g. cataracts). An accurate diagnosis is important to assist with appropriate medical monitoring and medical management of symptoms. In addition, genetic counseling should be made available to all patients because of the high risk of transmission. Potentially serious anesthetic risks are important to note, so the presence of this disorder should be brought to the attention of all medical providers.