This is a literature spontaneous report. A 77-year-old man presented with chief complaint of increased bruising at insulin injection sites for 1 week. Outpatient laboratory testing revealed a platelet count of 1000 per cubic millimeter; hence, he was admitted to the hospital for further evaluation and treatment. There was no reported history of fever or chills, abdominal pain, diarrhea, bleeding episodes, or neurological deficits. He was not exposed to any new medications or anticoagulants. There was no history of recent travel, camping, or mosquito or tick bites. His tacrolimus dose was not changed recently, and his blood pressure was under good control. The medical history was significant for end-stage renal disease secondary to hypertension and diabetes mellitus type 2. He was receiving hemodialysis for 1.5 years before he received a living unrelated kidney transplant 22 months previously. This was a 2A, 2B, 1DR human leukocyte antigen mismatch, with both donor and recipient serologic status positive for cytomegalovirus (CMV) infection. He received induction therapy with thymoglobulin (total dose of 5 mg/kg) and was maintained on triple immunosuppression with tacrolimus, mycophenolate mofetil (MMF), and prednisone. Six months after transplantation, he had developed of BK viremia, and his MMF was discontinued indefinitely. Other co-morbidities included coronary artery disease, anemia of chronic kidney disease, secondary hyperparathyroidism, and polyps observed during colonoscopy that were benign on histology. There was reported family history of bleeding or clotting disorders. Medications at the time of admission included allopurinol, amlodipine, aspirin, atorvastatin, carvedilol, cholecalciferol, fish oil, furosemide, hydralazine, insulin glargine, and aspart, lisinopril, prednisone, tacrolimus, and trimethoprim sulfamethoxazole. He received PREVNAR 13 vaccine around 1 month before admission. The initial physical examination showed normal vital signs. Systemic examination was unremarkable other than diffuse petechial rash in the areas of insulin injections over the lower abdomen and thighs. Laboratory testing resulted in hemoglobin, 11.7 g/dL and total white blood cell count, 7700/mm3, with normal differential and platelet count of 3000/mm3. His baseline hemoglobin level was 11.5 to 12.0 g/dL; white blood cell count, 7500/mm3; and platelet count, 140,000. Prothrombin time was 11.7 seconds, international normalized ratio was 1.11 and activated partial thromboplastin time was 30.9 seconds. Kidney function was at his baseline, with blood urea nitrogen of 31 and serum creatinine of 1.50. Thyroid stimulating hormone was 1.10. Lactate dehydrogenase and haptoglobin were normal, with no schistocytes, blasts, or dysmorphic cells observed on peripheral smear on 2 consecutive days. Blood and urine cultures, stool culture for shigella, CMV, BK virus, and Epstein-Barr virus detection in blood by polymerase chain reaction were negative. Tacrolimus trough level was 4.2 ADAM metallopeptidase with thrombospondin type 1 motif 13 (ADAMTS- 13) activity was 102%. Hospital course was reported as follows: with normal white blood cell count, hemoglobin, and kidney function at baseline, as well as the absence of schistocytes, blasts, or other dysmorphic cells on peripheral smear and negative infectious workup, the isolated thrombocytopenia was diagnosed as immune thrombocytopenic purpura. This was attributed to the PREVNAR 13 vaccine he received 1 month previously, because no other offending etiology could be identified. He was started on pulse dose steroids (methylprednisolone, 1000 mg intravenously) and pooled immunoglobulins (1 g/kg intravenously daily for 2 doses). He received 2 units of platelets on day 1, with platelet count increasing to 8000/mm3. He then received 4 more units of platelets the following day, with subsequent platelet count increasing to 74000/mm3. On day 4, platelet count increased to 94000/mm3, and he was discharged home on a tapering course of prednisone. Weekly outpatient blood counts showed continued improvement to his baseline of 140,000 over the next 3 weeks. The platelet count remained stable on follow-up for the past 10 months. The pathogenesis of ITP remains incompletely understood. Antibody production appears to be driven by CD4-positive helper T cells reacting to platelet surface glycoproteins, possibly involving CD40:CD40 ligand co-stimulation. Antibodies formed during viral or bacterial infections may also cross-react with normal platelet antigens (a form of molecular mimicry). Isolated cases of ITP have been reported with the administration of PCV13 vaccine, mainly in infants and young children ages 1 to 4 years. Reports of similar events in adult patients have been extremely rare. This case is further unique because ITP occurred in this patient, who was already on immunosuppression with a calcineurin inhibitor and corticosteroids.