Albuminuria in nondiabetic relatives of IDDM patients with and without diabetic nephropathy

Background. In non-insulin-dependent diabetes mellitus (NIDDM), there is a clustering of an elevated urinary albumin excretion rate (U-AER) in nondiab etic relatives of albuminuric patients. Whether this is also the case in in sulin-dependent diabetes mellitus (IDDM) is unknown. Methods. Overnight U-AER was measured in 186 nondiabetic first-degree relat ives of 80 IDDM patients with diabetic nephropathy (U-AER > 200 mu g/min or 300 mg/24 hours; DN+) and in 52 relatives of 25 IDDM patients without neph ropathy (U-AER < 20 mu g/min; DN-). The two groups of relatives were compar able regarding gender distribution, age, obesity, blood pressure, prevalenc e of antihypertensive therapy, and smoking habits. Results. No difference was found in overnight U-AER between relatives of pa tients with DN+ and DN- [median (range), 3.4 (0.1 to 372) vs. 4.0 (0.2 to 6 2) mu g/min, respectively, P = NS]. The proportion of relatives with a U-AE R = 10 mu g/min was 12% in DN+ compared with 8% in DN- (P = NS). Among rela tives of DN+, those with antihypertensive treatment (AHT+) had higher U-AER compared with those without [AHT+ vs. AHT-, 5.0 (0.5 to 372) vs. 3.4 (0.1 to 26.5) mu g/min, P < 0.01], a phenomenon that was not seen among relative s of DN-[AHT + vs. AHT-, 3.6 (2.1 to 24.3) vs. 4.0 (0.2 to 61.5) mu g/min, P = NS]. However, this analysis was impaired by the small number of relativ es of DN- with hypertension (N = 7). Conclusions. In IDDM, we found no clustering of elevated U-AER in nondiabet ic relatives of patients with nephropathy. This is different from what has been reported in NIDDM, and suggests heterogeneity in the genesis of albumi nuria in diabetes.