What systems are involved in Myotonic dystrophy type 1 (DM1?
• Cardiac. Conduction problems are a major cause of morbidity and mortality. About 90% of patients have ECG abnormalities, and complete heart block and sudden death are well recognized. Prophylactic pacemaker implantation is needed in patients with conduction block.
• Respiratory. Excessive daytime sleepiness is common because of a combination of weakness of the diaphragm and intercostal muscles, decreased response to hypoxia, alveolar hypoventilation, hypercapnia, and abnormalities of brain stem neuroregulatory mechanisms. Wicklund MP, Kissel JT: The limb-girdle muscular dystrophies. Neurol Clin 32:729-749, 2014. Trollet C, Gidaro T, Klein P et al.: Oculopharyngeal muscular dystrophy. 2001 Mar 8 [Updated 2014 Feb 20]. In: Pagon RA, Adam MP, Ardinger HH et al. (editors): GeneReviews ® [Internet]. Seattle (WA): University of Washington, Seattle; 1993–2015. Wicklund MP. The muscular dystrophies. Continuum 19:1535-1570, 2013.
• Gastrointestinal. Smooth muscle involvement results in many symptoms, including abdominal pain, dysphagia, emesis, diarrhea, and bowel incontinence.
• Central nervous system. Symptoms include impaired intelligence, apathy, and personality disorders.
• Skeletal muscle. Symptoms include atrophy, weakness, and myotonia.
• Endocrine. Testicular atrophy and insulin resistance are common; overt diabetes is uncommon.
• Other symptoms include frontal balding, cranial hyperostosis, air sinus enlargement, and minor sensory neuropathy.
