BACKGROUND: PIMS/MIS-C involves an innate immune response of the host against a trigger, in this case a virus, which causes hyperinflammation induced by a cytokine storm; this immune response is responsible for the systemic clinical manifestations and cardiac complications. The syndrome has been diagnosed usually between 2 and 6 weeks after infection by SARS-CoV-2; however, many patients have negative PCR (polymerase chain reaction) tests for the virus and positive immunoglobulin tests, suggesting that the syndrome appears in the early stages of convalescence from COVID-19. CASE REPORT: A 15-year-old female patient, previously healthy, with a history of close contact with a relative with COVID-19 confirmed by PCR 15 days before the onset of symptoms. He presented a 5-day history of fever, vomiting, and diarrheal stools; 48 hours later she presented with generalized asthenia, hyporexia and epistaxis. We evidenced elevation of immunoglobin G against SARS-COV-2 and negative PCR. In complementary tests, we evidenced elevation of inflammatory markers (CRP, procalcitonin, ferritin, D-dimer) and BNP; the echocardiogram revealed a condensation process in the pericardium, as well as coronary ectasia. Evolution: After confirming the diagnosis of PIMS/MIS-C, we started treatment with immunoglobulin, prednisone, and acetylsalicylic acid. On the fourth day of hospitalization, she presented diaphoresis and moderate pain in the epigastric region that did not subside; Abdominal CT revealed signs of mesenteric adenitis, which reconfirmed the proposed diagnosis. After completing 72 hours of treatment, and being evaluated again, she was discharged. We prescribed continuance of prednisone treatment and acetylsalicylic acid and 500 milligrams of amoxicillin orally every 8 hours. In addition, we recommended follow-up by the cardiology service one week after hospital discharge. The patient remains without complications after this episode. CONCLUSION: The diagnostic suspicion of PIMS/MIS-C must be present in all patients with characteristic symptoms, under the age of 20 years, with a history of contact with a positive COVID-19 patient and who in most cases will have a positive PCR test or positive serology. Given the multiple and variable clinical manifestations, it is important to take into account the differential diagnoses, especially Kawasaki Disease, whose clinical manifestations this syndrome mimics. Management and treatment depend on the patient's condition, but treatment with intravenous immunoglobulin is generally recommended; most patients respond to a single dose, as in the present case.