Background and objectives: Comorbidities greatly influence the course of many diseases. However, systematic data on comorbidities in patients with autoimmune encephalitis (AE) are scarce. We aimed to characterize comorbidities in patients with common AE variants and assess their influence on outcome and occurrence of infectious complications.
Methods: This multicenter, retrospective cohort study analyzed adult patients with definite anti-N-methyl-d-aspartate receptor (NMDAR), anti-leucine-rich glioma-inactivated-1 (LGI1), anti-contactin-associated protein-like-2 (CASPR2), and anti-immunoglobulin-like cell adhesion molecule-5 (IgLON5) AE registered by the GErman NEtwork for REsearch on AuToimmune Encephalitis between June 2004 and July 2023. Preexisting conditions (PECs), secondary diagnoses, and infectious complications documented during hospitalization were analyzed. Outcome was evaluated using a modified Rankin Scale (mRS), with unfavorable outcome defined as mRS >2 after a minimum of 12 months of follow-up.
Results: Among 308 patients with AE (144 NMDAR-AE, 98 LGI1-AE, 47 CASPR2-AE, and 19 IgLON5-AE), nearly half had cardiovascular and metabolic/endocrine, one-third neurologic, and one-fifth psychiatric comorbidities. Accompanying autoimmunity was observed in 12.7%. Univariable analysis showed that the presence of ≥3 PECs (OR 2.80, 95% CI 1.57-4.92), especially cardiovascular (OR 1.93, 95% CI 1.09-3.30) and psychiatric PECs (OR 3.84, 95% CI 1.96-7.31), was associated with unfavorable outcome. Multivariable regression analysis confirmed psychiatric PECs as independent risk factors (OR 4.55, 95% CI 1.99-10.60). During hospitalization, 13.6% of patients developed severe infections, although these were not associated with unfavorable outcome (OR 1.94, 95% CI 0.97-3.89). AE disease severity (OR 5.41, 95% CI 1.38-27.67) and intensive care unit admission emerged as the only independent predictors of severe infections (OR 20.76, 95% CI 7.02-75.10).
Discussion: As premorbid psychiatric conditions are main factors associated with unfavorable outcomes, these patients would highly benefit from integrated interdisciplinary treatment centers, or at least heightened awareness of these factors. Concomitant autoimmunity affecting other organs is frequent and should be sought. The risk of severe infections during the acute phase of AE is moderate and, given their lack of effect on outcome, should not justify withholding appropriate immunotherapy, even in elderly patients with comorbidities. Future prognostic models should incorporate comorbidities, particularly psychiatric ones, to enhance risk assessment and guide personalized care strategies.