Analysis of Serious Infections and Malignancy Risk in Myasthenia Gravis: A US Claims Database Study
Jana Podhorna1, Charlotte Ward2, Ikjae Lee3, Yuebing Li4, Tobias Ruck5, Elizabeth Teperov1, Ami Shah1, Jeff Guptill1
1argenx, Ghent, Belgium, 2ZS Associates, Evanston, Illinois, 3Columbia University, New York, New York, 4Cleveland Clinic, Cleveland, Ohio, 5Department of Neurology, Medical Facility, Heinrich-Heine-University Düsseldorf, Germany
Objective:
To characterize the incidence risk of serious infections and malignancies among adult myasthenia gravis (MG) patients compared to matched controls in the general population. 
Background:

N/A

Design/Methods:
This retrospective cohort study using Optum’s de-identified Market Clarity claims dataset (2015-2018) assessed incidence rate (IR) per 1,000 person-years and incidence rate ratio (IRR) for infections and malignancies between MG patients and propensity score-matched non-MG controls. Patients with malignancies (including malignant thymoma) within the 1-year lookback period were excluded.
Results:

The cohort consisted of 5,004 MG patients and 3,818 control patients. Most confounders were well-balanced between groups. MG patients were more likely to experience serious infections compared to controls (IRR = 1.83, 95% CI [1.54, 2.16]), especially sepsis (IRR = 1.84, 95% CI [1.38, 2.46]), pneumonia (IRR = 1.48, 95% CI [1.08, 2.02]), cellulitis (IRR = 1.84, 95% CI [1.12, 3.04]), and urinary tract infections (IRR = 1.79, 95% CI [1.17, 2.72]). They were also more likely to experience fatal infection (IRR = 2.57, 95% CI [1.29, 5.10]). Among opportunistic pathogens, the incidence risk of Candida (IRR = 1.52, 95% CI [1.26, 1.82]), Herpes zoster (IRR = 1.66, 95% CI [1.27, 2.17]), Klebsiella (IRR = 2.93, 95% CI [1.65, 5.22]), and Pseudomonas (IRR = 2.53, 95% CI [1.41, 4.54]) was also higher.

MG patients had an increased rate of some malignancies including thymic (IRR = 79.5, 95% CI [4.91, 1287.63]), skin (IRR = 1.46, 95% CI [1.19, 1.79]), male genital organs (IRR = 1.54, 95% CI [1.01, 2.33]), and CNS malignancies (IRR = 5.76, 95% CI [1.54, 21.51]). Malignancy-related death rate was not different between the groups.

Conclusions:
This study supports an increased risk for serious infections, opportunistic infections, and infection-related death in patients with MG. Besides the expected increased risk for thymic malignancies, MG patients had an increased risk of certain solid malignancies. 
10.1212/WNL.0000000000206555