Abstract
Severe thrombocytopenia is a rare adverse event of panitumumab. Here, we report the first patient with metastatic colorectal cancer who developed severe thrombocytopenia, diagnosed as panitumumab-associated drug-induced immune thrombocytopenia (DITP). A clinical diagnosis of DITP can be obtained by excluding other causes of thrombocytopenia and is confirmed by the recovery of thrombocytopenia after the discontinuation of the suspected drug. Treatment includes permanent discontinuation of the suspected drug. Re-exposure should be avoided. It should be kept in mind that panitumumab can induce DITP in the case of a new, sudden, unexpected, and isolated drop in platelet count after excluding other causes of thrombocytopenia.