["Seronegative" myasthenia gravis and antiMuSK positive antibodies: description of Spanish series]

Med Clin (Barc). 2005 Jun 18;125(3):100-2. doi: 10.1157/13076937.
[Article in Spanish]


Background and objective: Recently, the presence of antibodies to a muscle-specific tyrosine kinase (MuSK) has been reported in some patients with seronegative generalized myasthenia gravis. Our objective was to describe a group of patients who were positive for anti-MuSK antibodies.

Patients and method: Detection of antibodies using a radioimmunoassay was performed in the serum of 26 patients with generalized myasthenia gravis. We identified 9 patients with anti-MuSK antibodies (MuSK+). Clinical and therapeutic data from these patients were reviewed.

Results: Eight of nine patients were women aged between 20 and 40 years. Clinically, all of them showed prevalent bulbar signs, initially or during the progression of the disease. 77% of patients showed ocular involvement and 44% had symptoms of fatigability involving limbs. None of them improved upon thymectomy. Response to acetylcholinesterase inhibitors was variable. All of them responded to immunotherapy, although 30% required polytherapy.

Conclusions: The study of anti-MuSK antibodies defines a subgroup of patients, 34,61% in our series, with seronegative generalized myasthenia. This group is characterized by an homogenous clinical presentation with prevalent bulbar symptoms. The knowledge of the immunopathogenic mechanisms of anti-MuSK antibodies will allow a better understanding of both the variable response to acetylcholinesterase inhibitors and the absence of response to thymectomy in these patients.

Publication types

  • English Abstract

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Autoantibodies / immunology*
  • Cholinesterase Inhibitors / therapeutic use
  • Combined Modality Therapy
  • Diplopia / epidemiology
  • Extremities / physiopathology
  • Fatigue / epidemiology
  • Fatigue / physiopathology
  • Female
  • Humans
  • Immunotherapy
  • Male
  • Middle Aged
  • Myasthenia Gravis / epidemiology
  • Myasthenia Gravis / immunology*
  • Myasthenia Gravis / therapy
  • Receptor Protein-Tyrosine Kinases / immunology*
  • Receptors, Cholinergic / immunology*
  • Severity of Illness Index
  • Spain / epidemiology
  • Thymectomy
  • Treatment Outcome


  • Autoantibodies
  • Cholinesterase Inhibitors
  • Receptors, Cholinergic
  • MUSK protein, human
  • Receptor Protein-Tyrosine Kinases