Sirs, Nephrotic syndrome (NS) associated with autosomal dominant polycystic kidney disease (ADPKD) is observed only occasionally in adults [1,2], and it is extremely uncommon in childhood; to the best of our knowledge only three cases have been reported in the literature [3][4][5].We report a case of ADPKD associated with steroidsensitive NS in a 9-year-old boy, who was referred to the Nephrology Department with features of NS of 1 week's duration. He was born prematurely (28 weeks' gestation), suffered chronic lung disease, cerebral palsy with spastic quadriplegia and epilepsy (on sodium valproate), secondary to the neonatal problems. With regard to the family history, ADPKD was reported in his 51-year-old mother (current creatinine=325 μmol/l). NS was also reported in his older sister (now 24 years old), who presented at the age of 19 with renal biopsy confirmation of mesangiocapillary glomerulonephritis. Despite the fact that she continues to have significant proteinuria, she has stable renal function (current creatinine 80 μmol/l). NPHS2 (podocin) gene analysis showed no mutations. Furthermore, ADPKD was reported in his 22-year-old sister who, at the age of 18, presented with NS. No biopsy was performed because of the presence of multiple cysts. A presumed diagnosis of mesangiocapillary glomerulonephritis was made because of the family history. Her creatinine at presentation was significantly elevated, and within 3 years had progressed to end-stage renal disease (ESRD). Neither of the sisters received immunosuppressive therapy.On admission, the physical examination of the patient revealed facial puffiness and mild oedema. His blood pressure was 125/74 mmHg, and the urine output 2.0 ml/kg/h. Laboratory investigation showed normal serum creatinine (31 μmol/l; normal range 18-51 μmol/l) and decreased serum albumin (25 g/l, normal range 37-56 g/l). The protein to creatinine ratio in the early morning urine sample showed nephrotic range proteinuria (582.3 mg/mmol; normal <20 mg/ mmol). The urine dip testing revealed 3+ protein and 2+ blood. Serum complement C3 was 1.07 g/l (normal range 0.75-1.75 g/l) and C4 0.10 g/l (normal range 0.14-0.54 g/l) initially; later C4 was within the normal range. Anti-nuclear, anti-dsDNA, anti-glomerular base membrane and antineutrophil cytoplasmic antibodies were negative. Serology tests for hepatitis A and B were also negative.Ultrasound showed increased echogenicity of the renal cortex and the presence of multiple cysts of varying sizes in both kidneys. The right renal length was 10.5 cm (95th centile) and the left 9.3 cm (75th centile). No cysts were seen in the liver and spleen. Based on the typical ultrasound findings and the positive family history, a diagnosis of ADPKD was made. Renal biopsy was not performed because of the high anaesthetic risk in relation to the patient's underlying neurological problems.The patient was treated with prednisolone 2 mg/kg/day for 1 month, followed by 1 mg/kg on alternate days for 1 month and thereafter gradually discontinuing (total duration ...