Background: Pediatric venous thromboembolism is rare and usually associated with identifiable provocation. We report a complex case of multi-organ venous thrombosis mimicking acute infectious illness. Case presentation: A previously healthy 6 year old child presented with a 2 day history of fever, abdominal pain, headache, and vomiting. Initially managed as possible Dengue Fever, but child rapidly deteriorated with worsening of abdominal pain and distension, reduced urine output with oedema, fever, and altered sensorium. Biochemical evidence of acute kidney injury and adrenal crisis with metabolic derangement and hypoglycemia. Urgent ultrasonography and CT abdomen revealed extensive thrombosis of the intraabdominal Inferior Vena Cava (IVC), extending into the right hepatic vein and left renal vein, bilateral common iliac and right external iliac veins, evidence of bilateral adrenal infarction.Extended investigations done including genetics. Thrombophilia gene studies were negative. Paroxysmal nocturnal hemoglobinuria, sickle disease excluded. Autoimmune screening ANA came as highly positive, but dsDNA negative. Vasculitis and APLS excluded. Management optimized with multidisciplinary team comprising Pediatric Endocrinology , Hematology , Nephrology , Rheumatology and vascular surgery . Timely anticoagulation, coupled with aggressive management of adrenal crisis and acute kidney injury , led to a successful recovery . Conclusion: This case emphasizes the need for high clinical suspicion of extensive venous thrombosis with severe abdominal pain and rapid deterioration, even without provocative factors. Early imaging and prompt initiation of anticoagulation are crucial to prevent irreversible organ damage and mortality .