Myasthenia gravis with muscle specific kinase antibodies mimicking amyotrophic lateral sclerosis

Maartje G Huijbers, Erik H Niks, Rinse Klooster, Marianne de Visser, Jan B Kuks, Jan H Veldink, Pim Klarenbeek, Philip Van Damme, Marc H de Baets, Silvère M van der Maarel, Leonard H van den Berg, Jan J Verschuuren

Research output: Contribution to journalArticleAcademicpeer-review


Muscle-specific kinase (MuSK) myasthenia gravis (MG) is hallmarked by the predominant involvement of bulbar muscles and muscle atrophy. This might mimic amyotrophic lateral sclerosis (ALS) presenting with bulbar weakness. We encountered four cases of MuSK MG patients with an initial misdiagnosis of ALS. We analyzed the clinical data of the four misdiagnosed MuSK MG patients, and investigated the presence of MuSK autoantibodies in a group of 256 Dutch bulbar-onset ALS patients using a recombinant MuSK ELISA and a standard MuSK radioimmunorecipitation assay. Clues for changing the diagnosis were slow progression, clinical improvement, development of diplopia and absence of signs of upper motor neuron involvement. No cases of MuSK MG were identified among a group of 256 bulbar ALS patients diagnosed according to the revised El Escorial criteria. A misdiagnosis of ALS in patients with MuSK MG is rare. We recommend to carefully consider the diagnosis of MuSK MG in patients presenting with bulbar weakness without clear signs of upper motor neuron dysfunction.

Original languageEnglish
Pages (from-to)350-353
Number of pages4
JournalNeuromuscular Disorders
Issue number6
Publication statusPublished - Jun 2016


  • Amyotrophic lateral sclerosis
  • Myasthenia gravis
  • MuSK
  • Neuromuscular junction
  • IgG4


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