IgA and IgG2 deficiency associated with zonisamide therapy: A case report

Purpose: To report a previously undescribed adverse effect, IgA/IgG subclass deficiency associated with zonisamide (ZNS) therapy. Methods: Serum IgA and IgG subclass levels were determined by the turbidimetric immunoassay and enzyme-linked immunosorbent assay, respectively, in a 2-year-old boy with postmeningitis sequelae who was treated by ZNS. Results: Four months after initiation of ZNS, combined deficiency of IgA and IgG2 was noted. After cessation of ZNS, serum IgA level was promptly increased. IgG2 level was gradually increased, but remained subnormal after 7 months. Conclusions: This case documents, for the first time, the action of ZNS on IgG immune system as well as IgA system. If patients with ZNS therapy showed IgA deficiency and recurrent infections, it is preferable to check serum IgG subclass concentrations as well.