Prevalence and characteristics of patients with seronegative myasthenia gravis

Myasthenia gravis is an autoimmune disorder characterized by antibodies targeting the neuromuscular junction, causing fatigue of skeletal muscle. Natural history and epidemiological studies report that around 10% of patients diagnosed with myasthenia gravis do not have detectable levels of antibodies, categorized as seronegative. Theories of the pathophysiology in these patients are predominantly centered around undetectable antibody titers and antibodies against yet undefined antigens in the neuromuscular junction. This study aims to investigate the regional prevalence and characteristics of patients with seronegative myasthenia gravis. This study is a retrospective chart review of 350 patients with myasthenia gravis treated at the Copenhagen Neuromuscular Center. Of these, 15 (4.3%) were seronegative and 335 (95.7%) were seropositive. No differences were found when comparing the two groups on demographics, symptom profile, comorbidities, treatment, and diagnostic delay. The frequency of seronegative myasthenia gravis patients was lower in this cohort than previously reported. Seronegative myasthenia gravis patients were essentially indistinguishable from seropositive patients on all parameters evaluated. These findings correspond well with the emerging evidence of a similar pathophysiology in the two groups.