Myotonic Dystrophy - Symptoms and Signs

Symptoms and Signs

Presentation of symptoms and signs varies considerably by form (DM1/DM2), severity and even unusual DM2 phenotypes. DM1 patients often present with myotonia, disabling distal weakness and severe cognitive problems. DM2 patients commonly present with muscle pain, stiffness, fatigue, or the development of proximal lower extremity weakness (Day et al., 2003). The characteristic pattern of weakness is different for DM1 and DM2: In DM1, it is noted in face and jaw muscles, the drooping of the eyelids (ptosis), weakness of the neck muscles, hands and lower legs. In DM2, the weakness is more evident in proximal muscles, those closer to the trunk of the body: neck, shoulders, hip flexors and upper legs.

Symptoms and signs classically associated with DM1 are generally more mild and involve the smooth muscle (including G.I. symptoms), hypersomnia (daytime sleepiness), muscle wasting, dysphagia, and respiratory insufficiency. In addition, DM1 may manifest with a cognitive abnormalities including developmental delays, learning problems, language, speech, behaviour, apathy or hypersomnia. Cognitive manifestations for DM2 include problems with executive function (e.g., organization, concentration, word-finding) and hypersomnia. Conduction abnormalities are more common in DM1 than DM2, but all patients are advised to have an annual ECG. Both types are also associated with insulin resistance. Myotonic dystrophy patients may have a cortical cataract with a blue dot appearance, or a posterior subcapsular cataract.

DM2 is generally milder than DM1, with generally fewer DM2 patients requiring assistive devices than DM1 patients. In addition, the severe congenital form that affects babies in DM1 has not been found in DM2 and the early onset of symptoms is rarely noted to appear in younger patients in the medical literature.