Introduction: Cyanotic nephropathy is a chronic glomerular disorder occurring in patients with longstanding cyanotic congenital heart disease secondary to chronic hypoxemia. Hyper viscosity and glomerular hyperfiltration lead to glomerulomegaly , mesangial expansion, proteinuria, and progressive decline in eGFR. Case: 7-year-old boy with trisomy 21 with global developmental delay with uncorrectedTetralogy of Fallot (without prior Blalock- Taussig shunt) presented with facial puffiness and dyspnea of 3 days’ duration. He had a history of left-sided cerebral abscess requiring burr hole evacuation. On examination, he had dysmorphic features consistent with trisomy 21, including upslantingpalpebral fissures, epicanthic folds, flat nasal bridge, low-set ears, single transverse palmar crease. He had cyanosis, clubbing and ejection systolic murmur in pulmonary area with a soft second heart sound. Blood pressure was normal. Respiratory rate was 48/min with saturation of 60% on air, lungs clear. Abdominal examination revealed ascites and mild hepatomegaly . Neurological examination demonstrated residual right-sided weakness. Full blood count revealed Hb- 23.7g/dL, HCT-75.5%, plt-67 ,000 /μL, creatinine-87 μmol/L, blood urea 6.2 mmol/L. eGFR-45 ml/min/1.73m2. Urine albumin 3+, serum albumin 25 g/L. Urine proteincreatinine ratio-381.93 mg/mmol. Renal sonography revealed bilateral renal parenchymal changes. Echocardiogram- Teratology of Fallot, Bilateral SVC, IVC, hepatic vein congested with flow reversal, significant asymmetrical septal hypertrophy . He was managed with albumin infusions, angiotensin-converting enzyme inhibitors, and partial exchange transfusion. Conclusions: In cyanotic nephropathy , early corrective cardiac intervention reduces renal hemodynamic stress and may prevent progression. In established disease, management is supportive and focuses on control of hyper-viscosity , reduction of proteinuria, and optimisation of cardiac status.