Dose Adjustment of Intravenous Immunoglobulin Therapy With Serum IgG Monitoring to Prevent Hyperviscosity in a 13-Year-Old Boy With Kawasaki Disease.

Kawasaki disease (KD) primarily affects infants and young children, with cases in patients over 10 years of age being relatively rare. The standard treatment involves intravenous administration of high-dose intravenous immunoglobulin (IVIG) at 2 g/kg. In pediatric medicine, drug dosages are typically adjusted according to body size; however, in older children, body size-based dosing often results in excessively high doses, and adult dosages are frequently used as upper limits. Notably, no such upper limit exists for IVIG. Given that IVIG administration can cause severe cardiac and neurological complications due to hyperviscosity syndrome, careful dose management is essential. Here, we report the case of a 13-year-old KD patient weighing 53 kg who underwent repeated high-dose IVIG therapy. Serum IgG levels, total protein concentration, and hematocrit were monitored over time as an indicator of blood viscosity, allowing for dose adjustments. As a result, the patient successfully completed the treatment course without experiencing major adverse effects. Notably, the adjusted IVIG regimen effectively prevented the development of hyperviscosity syndrome. Furthermore, the patient did not develop coronary artery aneurysms, indicating that the treatment maintained both safety and therapeutic efficacy in managing Kawasaki disease. On the other hand, the increase in serum IgG levels following IVIG at a dose of 2 g/kg was greater in this patient compared to younger children receiving the same treatment. This case highlights the necessity of monitoring IgG levels to balance the efficacy and safety of IVIG therapy in older KD patients. However, there is no established threshold for IgG levels that would indicate a safe upper limit for IVIG administration, highlighting the need for further investigation.