The prognosis of MG patients with different thymic pathology: a multicenter retrospective cohort study

To identify the associations between thymic pathology and the prognosis of myasthenia gravis (MG) patients.

In this multicenter retrospective study, 1,254 myasthenia gravis (MG) patients who underwent thymectomy across four clinical centers were included. Participants were categorized by thymic pathology into thymomatous and non-thymomatous groups. Primary outcome was postoperative deterioration. Secondary outcomes comprised the proportion of patients achieving minimal manifestation status (MMS) within the first year after surgery and conversion from ocular MG (OMG) to generalized MG (GMG) within 2 years of symptom onset. Subgroup analyses assessed associations between world health organization (WHO) pathological type (both groups) or Masaoka stage (thymoma patients) and prognosis.

Thymomas were associated with an increased risk of deterioration in both Cox regression (adjusted HR = 1.40 [1.18, 1.66], p < 0.001) and logistic regression analyses (1-year deterioration: adjusted OR = 1.59 [1.15, 2.20], p = 0.005; 3-year deterioration: adjusted OR = 1.40 [1.01, 1.94], p = 0.047). Additionally, thymomas were linked to a higher conversion rate (adjusted OR = 2.37 [1.15, 4.86], p = 0.019). However, thymoma showed no significant association with MMS (adjusted p = 0.682). In the thymoma subgroup, neither pathological type nor Masaoka stage was significantly associated with deterioration (pathological type: 1-year p = 0.069, 3-year p = 0.220; Masaoka stage: 1-year p = 0.944, 3-year p = 0.909), first-year MMS attainment (pathological type: p = 0.067; Masaoka stage: p = 0.579), or conversion rate (pathological type: p = 0.606; Masaoka stage: p = 0.163). Similarly, in the nonthymomatous group, WHO pathological type was not significantly correlated with deterioration (1-year p = 0.806, 3-year p = 0.654), MMS achieved (p = 0.940), or conversion (p = 0.755).

This study demonstrated an association between thymoma and higher risks of clinical deterioration, which was independent of WHO pathological type or Masaoka stage.