A physical exam can identify the typical pattern of muscle wasting and weakness. It can also identify the presence of myotonia associated with DM1.
Laboratory tests can confirm the clinical diagnosis. They include electromyography (EMG). EMG involves inserting a small needle into the muscle to study electrical activity. EMG can detect muscle myotonia, suggesting the diagnosis.
The definitive diagnosis of DM1 is by a genetic test on a blood sample. The genetic test identifies the alterations in the DMPK gene causing DM1.
Getting a diagnosis of DM1 is complex, as the symptoms often mimic diseases that are more common. Lack of diagnosis is usually due to the symptoms not being recognised. Research has shown that there is also a tendency for those with the condition to underestimate their issues. As symptoms tend to increase with age, they are often attributed to the normal ageing process, as medical professionals are often unfamiliar with the condition. Individuals may visit several different specialists for treatment of a range of symptoms, further complicating the diagnostic process.
The multi-systemic nature of the decline, consistent with DM1 is often missed. This can be quite traumatic and can result in the patient not being identified as a candidate for palliative care.