Gemtuzumab-Ozogamicin-Related Impaired Hemoglobin-Haptoglobin Scavenging as On-Target/Off-Tumor Toxicity of Anti-CD33 AML Therapy: A Report of Two Cases

Figure 1

The clinical course of patient 1 (index case). Free plasma hemoglobin (P-Hb) and plasma lactate dehydrogenase (P-LD) are shown on the left y-axis, and white blood cell count (WBC) on the right y-axis. We used metronidazole and fidaxomicin to treat colitis caused by Clostridium difficile and valaciclovir for oral herpes simplex virus (HSV) infection. On day 21, blood culture (BC) was positive as the patient had Enterococcus faecium septicemia which continued the following weeks despite repeated removals and replacements of catheters and use of in vitro-effective antibiotics (tigecycline, linezolid, gentamicin, and daptomycin, which were selected because the patient was allergic to vancomycin). The patient tested positive for human herpes virus 6 nucleic acid test (HHV6-NAT) on day 25 and foscarnet was administered from day 31. Therapeutic plasma exchanges started on day 23 with transient responses to P-Hb and P-LD levels. The first signs of granulopoiesis were seen in bone marrow (BM) aspirate on day 46, and we were able to withhold TPEs after day 52, as the reaction subsided along with recovering hematopoiesis. Cumulative number of blood products transfused is shown below: there was no sign of hemolysis-related increased red blood cell (RBC) consumption, as we transfused the first RBC unit on day 25.