On the 15th of July, Alide Tieleman, neurologist at the Maasziekenhuis in Beugen and researcher at the Radboud University Medical Centre Nijmegen, will defend her thesis ‘Myotonic dystrophy type 2. A newly diagnosed disease in the Netherlands.’
Myotonic dystrophy type 2 (DM2; OMIM 602668) is a dominantly inherited neuromuscular disease characterized by mainly proximal muscle weakness, myotonia, cataracts and muscle pain. DM2 is caused by a tetranucleotide (CCTG) expansion in intron 1 of ZNF9 gene located on chromosome 3q21.3. In 2004 the first Dutch DM2 family was described. This thesis is the result of a nationwide, bottom-up designed research into the clinical picture of genetically identified patients with DM2, including the patients’ perspective in the assessment of the impact of the disorder.
The first part of the thesis concerns clinical studies in DM2 patients, adult-onset DM1 patients (disease controls) and healthy controls. Using the Dutch Gastrointestinal Symptoms Questionnaire we found that gastrointestinal involvement is frequent in DM2 (dysphagia for liquids (38%) and solid food (41%), abdominal pain (62%), and constipation (62%)), and may be attributed to any part of the gastrointestinal tract. Radiological measurement of colon transit time was increased in 24% of DM2 patients. In DM2 patients who reported difficulty in swallowing the presence of dysphagia could be confirmed, clinically as well as by fiberoptic endoscopic evaluation of swallowing. Dysphagia is generally mild, and do not lead to weight loss, or aspiration pneumonia in DM2 patients.
Sleep quality, measured with the Pittsburg Sleep Quality Index, was poor in DM2 patients, and was mainly due to sleep disturbances as a result of nocturnal pain. DM2 patients experienced severe fatigue, comparable with the DM1 group. In striking contrast with DM1, excessive daytime sleepiness was not present in DM2.
The second part presents the results of additional investigations. The observation of a strong association between DM2 and autoimmune diseases was described and possible explanations for this new association were proposed.
In order to determine the presence and extent of muscle changes in DM2 muscle ultrasound examinations were performed on seven muscles in DM2 and adult-onset DM1 patients. In DM2 all examined muscles showed significantly increased echo intensities. Muscle thickness was more decreased in the proximal arm muscles in DM2 compared to DM1. Echo intensity sum score correlated positively with age and negatively with quantitatively measured muscle force in both DM types.
Health status was measured with the SF-36, and we determined its relationship with pain and fatigue. The results showed the impact of DM2 on a patients’ physical, psychological and social functioning is significant and as high as in adult-onset DM1 patients. Symptomatic treatment of pain and fatigue may decrease disease impact and improve health status in DM2, even if the disease itself can not yet be treated.
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