Higher Prevalence of SLE in Patients With Myasthenia Gravis

Myasthenia gravis (MG) is associated with an increased risk for systemic lupus erythematosus (SLE), according to study results presented at the American College of Rheumatology (ACR) Convergence 2021, held virtually from November 3 to 10, 2021.

Both SLE and MG are autoimmune disorders with similar features and may coexist, especially among young women. However, limited epidemiology data exist on the association between MG and SLE.

The objective of the current study was to determine the prevalence of SLE among patients with MG and to assess the differences between patients with MG who developed SLE preceding or following an MG diagnosis.

The IBM Explorys database was used to identify data from more than 60 million patients in the US, with International Classification of Diseases, Ninth Revision (ICD-9) codes used to define SLE and MG. The cohorts were further stratified by age, race, sex, smoking status, thymectomy, and autoimmune and other comorbidities. Index date was defined as date of SLE diagnosis in patients with MG.

Among a total of 59,896,040 patients, prevalence rates of SLE and MG were 0.1% and 0.04%, respectively.

The current retrospective observational study included 26,110 patients with MG, including 370 patients (89.19% women) with SLE, and 65,000 control participants with lupus (90.61% women).

Lupus was more common among patients with MG (n=370/26,110; 1.42%), than control participants (n=65,000/59,869,730; 0.11%) and a diagnosis of MG was associated with more than 10-fold increased risk for SLE (odds ratio, 13.8; 95% CI, 2.08-14.84; P <.0001).

Several risk factors were identified for SLE among patients with SLE and MG vs those with MG only, including the female sex (89.19% vs 54.53%, respectively; P <.0001), African American ethnicity (18.92% vs 10.76%, respectively; P <.0001), total (8.11% vs 2.64%, respectively; P <.0001) and partial (5.4% vs 1.89%, respectively; P <.0001) thymectomy, autoimmune diseases, as well as type 1 diabetes (8.11% vs 3.19%, respectively; P <.0001), cerebral infarction (16.22% vs 8.19%, respectively; P <.0001), and chronic obstructive lung disease (24.32% vs 14.1%, respectively; P <.0001).

“Patients [with MG] should be evaluated for the coexistence of SLE especially in post-thymectomy patients and the young African American women with a history of other autoimmune diseases. Additionally, assessment for MG is suggested in patients [with lupus] with unexplained muscular weakness,” the researchers concluded.

Reference

Merjanah S, Igoe A, Kaelber D, Scofield RH. Association between systemic lupus erythematosus and myasthenia gravis: a population-based national study. Presented at: ACR Convergence 2021; November 3-10, 2021. Abstract 0334.