Monocyte-to-HDL Cholesterol Ratio and Complete Blood Count-Derived Inflammatory Markers in Myasthenia Gravis: A Cross-Sectional Case–Control Study

Background/Objectives: We evaluated the monocyte-to-high-density lipoprotein (HDL) cholesterol ratio (MHR) and complete blood count (CBC)-derived inflammatory ratios in myasthenia gravis (MG). Methods: In this cross-sectional case–control study, 80 patients with MG and 87 controls were compared. MHR, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), lymphocyte-to-monocyte ratio (LMR), and systemic inflammation response index (SIRI) were analyzed with Mann–Whitney U tests, ROC analysis, and multivariable logistic regression with covariates selected using a directed acyclic graph. Results: MHR was higher in MG (median 0.0091 vs. 0.0058; q < 0.001), as were NLR, PLR, and SIRI, whereas LMR was lower. AUCs were 0.779 (SIRI), 0.774 (LMR), and 0.700 (MHR). Each 0.001-unit increase in MHR was associated with 1.23-fold higher odds of MG (95% confidence interval 1.11–1.38; p < 0.001), and adding MHR to the covariates increased the model area under the curve from 0.752 to 0.823 (p = 0.017; complete-case analysis, p = 0.216), mainly through the monocyte count. No marker correlated with severity (all p > 0.12). Conclusions: MHR and CBC-derived ratios differed between patients with MG and controls independent of demographic and metabolic covariates, largely reflecting monocyte counts, but were not associated with severity and do not appear suitable for disease monitoring.