Abstract
The current study presents the case of a 9-year-old Chinese boy who presented with eosinophilia and elevated serum levels of immunoglobulin G4 (IgG4). A bone marrow puncture identified an elevated eosinophil rate of 23% (normal range, <5%), which indicated eosinophilia. However, gene analysis, fluorescent in situ hybridization and other examinations, including bone marrow aspiration, blood routine, auto-antibody tests and parasitic and allergens screening, contradicted a diagnosis of secondary or clonal eosinophilia. Furthermore, the patient exhibited multiple lymph node swelling and a lymph biopsy strongly indicted a pathological diagnosis of IgG4-related disease (IgG4-RD). His peripheral blood flow cytometry confirmed an elevated count of plasmablasts, which is specific to IgG4-RD. The patient responded well to therapy with prednisone and remained healthy in all follow-ups. By taking all these factors into consideration, the boy was diagnosed with IgG4-RD. It is difficult to distinguish IgG4-RD from hypereosinophilic syndrome and the potential association between the two remains unclear. However, the present case study serves as a reminder that IgG4-RD may occur in children and medical professionals should not neglect this possibility.