Familial clustering of diabetic nephropathy in Brazilian type 2 diabetic patients

There is evidence for genetic predisposition to diabetic nephropathy in type 1 diabetic patients. However, there are few studies on type 2 diabetic patients, and most of those have been conducted on ethnic minorities or Caucasian individuals. The aim of this study was to ascertain the presence of an inherited predisposition to diabetic nephropathy in a sample of Brazilian type 2 diabetic patients. Families with two or more type 2 diabetic siblings were identified. Subjects with the longest duration of known diabetes were considered probands. Some 90 probands and their 107 diabetic siblings were studied. Urinary albumin excretion rate was measured in a sterile 24-h urine sample on at least three different occasions. Probands and siblings were classified according to urinary albumin excretion rate as normo- (<20 microg/min), micro- (20-200 microg/min), or macroalbuminuric (>200 microg/min). Patients with end-stage renal disease were included in the macroalbuminuric group. Macroalbuminuria was identified in 5.2% of the siblings of normoalbuminuric probands and in 24.1% of the siblings of macroalbuminuric probands (P = 0.024). In multiple logistic regression, the presence of diabetic nephropathy in probands (micro- or macroalbuminuria and end-stage renal disease) was significantly associated with the presence of sibling diabetic nephropathy (odds ratio = 3.75, 95% CI = 1.36-10.40, P = 0.011) adjusted for proband fasting plasma glucose and diabetes duration. Interpretation of these results should take into account the possibility that the families including siblings with diabetic nephropathy may have been overcounted and, on the other hand, that the siblings without diabetic nephropathy may have been undercounted. In conclusion, there is a familial aggregation of diabetic nephropathy in this sample of type 2 diabetic patients.