She denies any cramping, dark coloured urine, weakness, muscle atrophy, bowel or bladder dysfunction, viral illnesses, tremor, unexplained falls, musculoskeletal pain, or toxic exposures. Her husband reports that he has never noticed his wife's muscles twitching while she is sleeping. There is no family history of early onset diabetes, cataracts, frontal balding, or neurological disorders. She is a social drinker and denies illicit drug use. She has one daughter aged 2 who is healthy.
Review of systems is unremarkable.
If necessary, revise your differential diagnosis based on the additional clinical history. There is little support for a clinical diagnosis of myotonic dystrophy, however a congenital myotonia cannot be excluded. Stiff person syndrome, Isaac's syndrome, or even the possibility of malingering should still be considered. Involvement of the abdominal muscles and resolution of symptoms with sleep would lean towards a diagnosis of stiff person syndrome or malingering.