Objective:

n/a

Background:

A 46-year-old woman presented to the neurology clinic for evaluation. She had an abnormal MRI brain with multiple white matter lesions, including some periventricular and juxtacortical lesions due to which she had been diagnosed with multiple sclerosis (MS). It was unclear why she had bilateral anterior temporal white matter FLAIR hyperintensities as she did not have clinical features of CADASIL or mitochondrial myopathy. She had progression of symptoms over the seven years prior with distal symmetric arm and leg weakness, fatigue, and stiffness in her hands followed by proximal extremity weakness, dysphagia, orthopnea, and monocular diplopia. 

Design/Methods:

n/a

Results:

Given that her symptomatology and exam were not consistent with an upper motor neuron disorder, an EMG/NCS was obtained and this revealed myotonic potentials in several muscles raising suspicion for a myotonic disorder. She had no definite family history but her father had died of cancer at age 45. Subsequent genetic testing was significant for >150 repeats in the DMPK gene, confirming a diagnosis of myotonic dystrophy type 1 (DM1).

Conclusions:

This case highlights a diagnostic challenge for neurologists as the white matter lesions associated with DM1 frequently overlap with MS, CADASIL, and mitochondrial myopathy. Diagnostic accuracy is vital as patients with DM1 require multidisciplinary medical care to prevent morbidity and mortality.