Case history
Case history #1
A 25-year-old woman presents with recurrent slurring of speech that worsens when she continues to talk. She has trouble swallowing, which deteriorates when she continues to eat, and has double vision that gets worse when sewing, reading, or watching TV. She reports that her head is heavy and hard to hold up. Her symptoms have progressively deteriorated over the past 6 months. She has intermittent weakness in her legs and arms. She is fearful of falling due to her legs giving way and she has trouble combing her hair or putting on deodorant. She reports a feeling of generalised fatigue and is occasionally short of breath.
Case history #2
A 76-year-old man reports double vision for the past 2 months. Within the past 2 weeks he has developed bilateral ptosis (drooping eyelids). His ptosis is so severe at times that he holds his eyes open to read. He is unable to drive due to the ptosis and diplopia (double vision). His symptoms are generally better in the morning and get worse throughout the day.
Other presentations
MG usually presents with one of three different forms: ocular, oropharyngeal, or generalised. Approximately 50% of patients present with purely ocular symptoms (ptosis, diplopia): so-called ocular myasthenia.[22] Between 50% and 60% of those who present with purely ocular symptoms will progress to develop generalised disease, and the vast majority will do so within the first 1 to 2 years. Overall, 15% to 20% of MG patients will experience a myasthenic crisis (exacerbation necessitating mechanical ventilation), which usually occurs within 2 years of diagnosis.[23]
The subset of patients with antibodies directed against muscle-specific tyrosine kinase (MuSK) present with one of three phenotypes (the first two are considered characteristic): severe faciopharyngeal weakness, with atrophy of involved muscles in long-standing disease; predominant neck and respiratory weakness with frequent progression to crisis, or; clinical features indistinguishable from non-MuSK-MG.[5][24]
Some patients with ocular MG without detectable acetylcholine receptor (AChR) antibodies have been reported to have MuSK antibodies.[25]
The clinical phenotype of LRP4- and agrin-antibody-positive MG is not clear. There have been some reports that patients with LRP4 and/or agrin antibodies have mild disease, but mild to moderate generalised MG has been described in others, similar in pattern to that for most AChR-antibody-positive patients.[10][11][12][13][26][27][28][29]
The clinical importance of antibodies to collagen Q and cortactin is not yet clear.
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