Leukopenia and thrombocytopenia in immunoglobulin G4-related disease: frequency, severity, and the association with splenomegaly.

Hematological abnormalities are not generally considered characteristic of immunoglobulin (Ig)G4-related disease (IgG4-RD). This study investigated the frequencies of leukopenia and thrombocytopenia in IgG4-RD and the clinical factors associated with their development. We retrospectively analyzed 56 patients diagnosed with IgG4-RD between April 2015 and July 2024 according to the 2020 revised comprehensive diagnostic criteria. Clinical characteristics were compared between patients with and without thrombocytopenia and splenomegaly. Independent factors associated with thrombocytopenia were evaluated using binomial logistic regression. Leukopenia and thrombocytopenia occurred in 6 (10.7%) and 24 (42.8%) patients, respectively. Marked thrombocytopenia (platelet count <10.0 × 104/μL) was observed in 11 patients (19.6%). Patients with thrombocytopenia were older, more often male, and more likely to have splenic and aortic involvements, with significantly higher serum IgG levels. Splenomegaly was associated with increased frequencies of leukopenia and thrombocytopenia, as well as lower platelet and lymphocyte counts. Multivariate analysis identified older age as consistently associated with thrombocytopenia, while splenomegaly was independently associated with thrombocytopenia and marked thrombocytopenia in selected models. Most patients treated with glucocorticoids showed improved blood cell counts within 12 weeks. Thrombocytopenia may be common in IgG4-RD, and splenomegaly and older age are associated with thrombocytopenia.