Fatal anaphylaxis due to alpha-gal syndrome after initial cetuximab administration: The first forensic case report.

Cetuximab is mainly used for the treatment of advanced and metastatic colorectal cancer. Owing to the oligosaccharide galactose-α-1,3-galactose (α-gal) in its heavy chain, cetuximab can induce severe IgE-dependent anaphylaxis. α-Gal is also the antigen responsible for α-gal syndrome, known as mammalian meat allergy. Patients with α-gal syndrome may suffer from cetuximab-induced anaphylaxis at the first administration because of developed α-gal-specific IgE antibodies. A male patient in his 50 s with metastatic colon cancer was receiving chemotherapy involving scheduled cetuximab administration. However, he died soon after the first administration. Forensic autopsy confirmed rectal cancer, metastatic rectal cancer in the liver, and renal cancer. Laboratory blood tests revealed the presence of cetuximab- and beef-specific IgE antibodies before cetuximab administration and an extremely high level of tryptase after administration. Thus, we determined that the death was caused by cetuximab-induced anaphylaxis due to the preexisting α-gal syndrome. To the best of our knowledge, this is the first autopsy case report in forensic medicine of fatal anaphylaxis after initial cetuximab administration.