MO052COL4A3/COL4A4 AS A CAUSE OF MULTICYSTIC KIDNEY DISEASE

Abstract

Abstract Background and Aims Thin basement membrane nephropathy (TBMN), the most common cause of persistent microhaematuria (mH), is due to mutations in genes codifying alfa-3 and alfa-4 collagen IV chains (COL4A4/COL4A3). Initially considered as a benign condition, subsequent studies have shown that an important number of patients develop proteinuria and CKD. We reported in a previous small study the presence of multicystic kidney disease (MCD) in some TBMD patients. In this study we aimed to evaluate the presence of MCD in a larger cohort of TBMD patients and analyze its association with renal outcomes. Method We collected 50 patients with a diagnosis of TBMD based on the presence of persistent mH (>5 erythocytes per high power field in more than 90% of urinary sediments and radiological examinations to exclude other causes of mH) and at least one first-degree relative with persistent mH. TBMD diagnosis was confirmed by renal biopsy (glomerular basement membrane thickness less than 150nm) in 18 patients and by genetic test (pathogenic mutations in COL4A3/COL4A4) in 6 patients. MCD was diagnosed by the presence of uncountable cysts on renal ultrasonography. Results Mean age at diagnosis was 43.7 years, 34% were males and 18% had hypertension. At baseline, serum creatinine (SCr) was 0.9 mg/dL, proteinuria 0.48 gr/24h and 9 patients (18%) had CKD (estimated glomerular filtration rate -eGFR- lower than <60 mL/min/1.73m2). 7 patients (14%) had CKD G3 and 2 (4%) CKD G4. Kidney cysts were found in 34 patients (68%) and 19 (38%) met MCD criteria. After a mean follow-up of 14.7±11.5 years, 23 patients (46%) had CKD. Among them, 17 patients (34%) had CKD G3, 2 (4%) CKD G4, and 4 (8%) CKD G5. Hypertension was more frequent among CKD patients as compared with no-CKD patients (39 vs 0%, p 0.00), proteinuria was higher (0.58±0.68 vs 0.39±0.58 g/24h, p 0.05) and MCD more frequent (65.2% vs 14.8%, p 0.00). Patients with MCD had higher SCr (2.1 vs 1.1 mg/dL, p 0.004) and lower eGFR (41.7 vs 77.2 mL/min/1.73m2, p 0.00) at the end of follow-up, and MCD was the only risk factor for the occurrence of CKD (OR 6.49, 95% CI 1.3-31.6) by multivariable analysis that included age, hypertension and proteinuria. Conclusion MCD is frequently observed in TBMD patients and is a risk factor for the progression of CKD.