Autoimmune myasthenia with anti-MuSK autoantibodies (about 8% of patients) has a unique phenotype, as does its response to treatment, particularly anticholinesterase drugs. The results of a retrospective study carried out in Italy on 202 patients followed up at an expert center demonstrate this:
- 81.6% of them were already on anticholinesterase medication prior to admission,
- of these, only 4.2% experienced an initial benefit, while 33.9% reported an exacerbation of muscle weakness,
- 76.9% reported at least one of the classic side effects of these drugs, and 7.3% had a cholinergic crisis.
For the Italian authors, these data suggest that anticholinesterase drugs should be avoided in myasthenia with anti-MuSK. When the result of the autoantibody test is not known at the time of the first prescription, anticholinesterase treatment should be accompanied by early evaluation, and the occurrence of side effects (especially at low dosage) should raise suspicion of this subtype of myasthenia.
