Genetic polymorphisms of the renin-angiotensin system and complications of insulin-dependent diabetes mellitus

OBJECTIVE

Patients with insulin-dependent diabetes mellitus (IDDM) have a high risk of developing diabetic nephropathy, retinopathy and cardiovascular diseases. The contribution of gene polymorphisms of the renin angiotensin system to these complications is controversial and may differ among populations.

METHODS

In 257 Dutch IDDM patients (188 with urinary albumin excretion (UAE) <30 mg/24 h), logistic regression analysis was used to study the relationships among, on the one hand, the insertion/deletion gene polymorphism of the angiotensin-converting enzyme gene (ACE-ID), the M235T gene polymorphism of the angiotensinogen gene (AGT-M235T), and the A1166C gene polymorphism of the angiotensin type 1 receptor gene (AT1-A1166C), and, on the other hand, UAE, retinopathy, hypertension, and coronary heart disease.

RESULTS

The T-allele of the AGT-M235T polymorphism was associated with an increased risk of an elevated UAE (odds ratio (OR) 3.03; 95% confidence interval (CI) 1.06-8.61), but only when interaction with the D-allele of the ACE-ID polymorphism was considered. A previously described positive interaction between the T-allele of the AGT-M235T polymorphism and the D-allele of the ACE-ID polymorphism could not be confirmed. The T-allele was also associated with an increased risk of retinopathy (OR 3.89, 95% CI 1.79-8.47). The CC-genotype of the AT1-A1166C polymorphism was associated with hypertension (OR 3.58; 95% CI 1. 23-10.37).

CONCLUSIONS

In a Dutch IDDM population, including 69 patients with (incipient) diabetic nephropathy, the T-allele of the AGT-M235T polymorphism is associated with an elevated UAE and diabetic retinopathy and the CC-genotype of the AT1-A1166C polymorphism is associated with hypertension. A previously described interaction between the AGT-M235T and the ACE-ID polymorphisms could not be confirmed. Since the number of nephropathic patients in this study is small, these conclusions must be interpreted with caution.

HIV-related thrombotic thrombocytopenic purpura: report of 2 cases and a review of the literature

Thrombotic thrombocytopenic purpura (TTP) is a syndrome characterised by the clinical pentad of microangiopathic haemolytic anaemia (MAHA), thrombocytopenia, renal failure, fluctuating neurologic signs, and fever. The aetiology of TTP is unknown, but associations with various underlying diseases, infections and drugs have been identified. One of these associations is with HIV infection. We describe the clinical picture, the laboratory results and the response to plasma therapy of two cases of HIV-associated TTP. In both patients, a longitudinal semiquantitative assessment of the numbers of schistocytes in blood was made, which correlated well with the more traditional parameters of disease activity. Since 1987, at least 49 patients with HIV-associated TTP have been reported. A case-analysis of the 38 patients who were described in sufficient detail and a review of the literature in the setting of HIV infection is presented. The most important conclusions from these combined data are: (1) TTP usually seems to occur in patients with a CD4+ lymphocyte count < 250 x 10(6).l(-1); (2) more than 50% of the patients present with TTP soon after or during an infectious or malignant disease; (3) plasma exchange is the therapy of choice, still resulting in mortality of 22%; (4) higher initial platelet count and creatinine level are correlated with an adverse outcome.