Rare side effect caused by atezolizumab, an immune checkpoint inhibitor: Cold agglutinin disease.

With the increasing use of immune checkpoint inhibitors, the variety of side effects has increased and case reports have increased. After detection of cold agglutinin, IgG, cryoglobulin, mycoplasma pneumonia, hepatitis B, hepatitis C and HIV were found negative in the differential diagnosis, Our case appears to be immune checkpoint inhibitor-related Cold Agglutinin Disease (CAD). It should not be forgotten that immune checkpoint inhibitors, which are widely used, may cause CAD, and hemoglobin-hematocrit discordance should be paid attention to in routine controls.