Case Presentation: 70 year old male veteran with Lung Adenocarcinoma, Chronic Obstructive Pulmonary Disease, and remote Mucosa Associated Lymphoid Tissue Lymphoma presents with nausea, diaphoresis, and shortness of breath following administration of intravenous Iodinated Contrast Media (ICM) obtained for a staging Computerized Tomography (CT) scan. The patient was afebrile, with sinus tachycardia at 120 beats per minute, blood pressure 143/74, respiratory rate 16, pulse oximetry 98% on room air. No wheezing, throat edema, or urticaria was present. Symptoms resolved spontaneously. In further discussion, the patient reported prior symptoms after ICM. Physiologic contrast reaction was diagnosed.The patient underwent the CT scan at 3:58pm. Blood collected at 5:10pm showed normal white blood cell count and hemoglobin, but platelet count of 28,000 platelets per microliter. A level the following day was 6,000 platelets per microliter. Petechiae were visible across the chest and extremities.A peripheral blood smear demonstrated no schistocytes and rare platelets. Evaluation for syndromes associated with thrombocytopenia was negative. Contrast Induced Immune Thrombocytopenia (ITP) was diagnosed. The patient was treated with Dexamethasone 40mg daily, and platelets rose appropriately. The patient has remained free of ITP.

Discussion: This patient was diagnosed with a physiologic rather than allergic-like reaction from ICM. This type of reaction is believed to be due to direct chemotoxicity and osmotoxicity. They increase in severity with increasing dose and concentration of ICM. This patient received a high dose of ICM due to need for full staging CT scans, and thus was at an elevated risk of developing a physiologic reaction. Allergic-like reactions are labeled as such because an antigen-antibody response cannot always be identified. Skin allergy testing is commonly negative.ITP is an immune-mediated, isolated thrombocytopenia (platelet count < 100,000 microliters) in which the clinical scenario and laboratory testing do not reveal other etiologies. In this patient, there was no recurrence of lymphoma, and an evaluation for microangiopathic processes and viral infections were negative. Treatment for ITP is determined by its symptoms and severity, the mainstay of treatment being steroids, and without appropriate response, Intravenous Immunoglobulin.ICM as a cause of ITP is rare, but has been previously described. The mechanism of immune activation is not known, and it tends to be accompanied by either allergic-type or physiologic reactions, as was seen here. In multiple case reports there is often seen a dramatic decline in platelet levels. This patient’s abnormal platelet count 1 hour following the ICM is not unexpected. While there is thought that the ITP may spontaneously resolve in the absence of ICM, the cases of ITP reported showed platelet levels requiring immediate treatment.

Conclusions: CT scans with ICM have become increasingly safe and effective with lower doses of ICM required. However, with the near ubiquity of patients undergoing CTs, hospitalists must be vigilant for adverse effects. Identifying physiologic versus allergic-like reactions will change management. ICM induced ITP is a rare but important syndrome as a precipitous drop in platelets can occur. After a thorough history, medication review, physical exam, laboratory analysis, and treatment, it is important for clinicians to document the allergy and be more judicious in future use of ICM in these patients.