Rituximab (RTX) is effective for treating childhood refractory
nephrotic syndrome (NS), such as
steroid-dependent (SD), frequently relapsing (FR), and
steroid-resistant (SR) NS. While RTX has been proven to be effective in treating SDNS, FRNS, and SRNS, it may cause
serum sickness, a rare illness characterized by
fever,
rash, and
arthralgia, 10-14 days after primary
antigen exposure or within a few days after secondary
antigen exposure, by producing human anti-chimeric
antibodies (HACAs). A 17-year-old girl with refractory SDNS treated with RTX and oral
cyclosporine A was admitted with
fever and
arthralgia 10 days after the fifth RTX dose was administered. After RTX was started when she was 14-years-old, SDNS remission was then achieved, and
prednisolone was discontinued. Although
antibiotics and
non-steroidal anti-inflammatory agents were administered,
fever and
arthralgia continued. After various inspections and
clinical course, we considered her as RTX-induced
serum sickness (RISS). The patient had an elevated HACA level and was diagnosed with RISS.
Fever and
arthralgia disappeared 5 days after onset. To the best of our knowledge, this is the first reported case of RISS with NS.
Fever,
rash, and
arthralgia after RTX administration can be the initial symptoms.