Myotonic Dystrophy

DM1 Four types:  adult-onset, congenital, childhood-onset and late-onset oligosymptomatic   The younger the onset, the more severe the symptoms Core symptoms: myotonia progressive muscle weakness cataracts     Other symptoms: muscle atrophy cardiac conduction defects and/or tachyarrhythmia neurological symptoms: behavioural changes, cognitive impairment and hypersomnia  gastrointestinal problems: constipation, diarrhoea and incontinence balding (typically in men) fertility problems ptosis type II diabetes  Sudden cardiac death as a result of heart problems can occur in approximately one third of patients  Women also have a greater risk of complications during pregnancy: miscarriage, premature labour, prolonged labour, placenta previa and post-partum haemorrhage  DM2  generally milder form of the disorder with a more variable clinical phenotype Myotonia can be absent in DM2 patients first symptom typically muscle weakness of the proximal limbs Unlike DM1, DM2 does not have severe childhood forms, and prognosis is generally good with typically no reduction in life expectancy seen  greater prominence of severe myalgic pain

Autosomal dominantDM1 DMPK gene expansion of >50 CTG repeats is pathogenic Expansion of repeats is rare, most people inherit repeats from affected parent DM2  CNBP gene CCTG repeat  Repeats tend to contract on transmission and then expand as the individual ages Do not see expansion upon transmission

Clinical features

genetics