Walsh & Hoyt: Localized or Ocular Myasthenia

Although 5075% of patients with MG initially present with so-called ""ocular MG,"" with only ptosis, diplopia, or both, 5385% of these patients eventually develop other signs and symptoms of ""clinically generalized MG,"" including proximal muscle weakness, difficulty with speech, and difficulty swallowing. Thus, only a remainder of 1547% of patients whose manifestations remain localized to the eyelids and extraocular muscles continue to have ocular MG. The percentage of patients with only ocular manifestations at onset who go on to develop systemic manifestations within 2 years is 4387%. Grob estimated from his well-analyzed, large experience that when the disease had remained localized for a year from onset, the likelihood of remaining localized was 84%. Age and sex are not reliable indicators of the risk of progression of disease. The presence of positive anti-ACh receptor antibodies may increase the risk of generalization. The absence of single-fiber EMG abnormalities in limb muscles has been associated with a reduced risk of progression to clinically generalized MG, but the presence of such abnormalities does not significantly increase the risk of generalization over the baseline likelihood.