Preclinical and manifest diabetes mellitus in young patients with Friedreich's ataxia: no evidence of immune process behind the islet cell destruction

Friedreich's ataxia is known to be associated with diabetes mellitus in up to 20% of the patients. However, type, development and course of diabetes mellitus are not well characterised. We report on 3 patients (2 female and 1 male, age 13-20 years) with the combination of Friedreich's ataxia and diabetes mellitus. Diabetes mellitus was characterised as follows: (1) it was strictly insulin-dependent and ketosis-prone, (2) the average insulin requirement was 1 U/kg body weight, (3) the HLA haplotype was not typical of Type 1 (insulin-dependent) diabetes mellitus, (4) there were no positive immune parameters typical of Type 1 diabetes at the clinical onset of diabetes mellitus and (5) there was no remission. To evaluate a preclinical phase as in common autoimmune Type 1 diabetes, i.v. glucose tolerance tests (0.5 g glucose/kg body weight) were performed in 8 patients with Friedreich's ataxia without diabetes mellitus. Seven patients had normal early phase insulin response. In contrast, the glucose disappearance rate was slow in 4 and normal in 3 patients. One of the 8 patients showed a prediabetic metabolic state: the early-phase insulin response was abolished and the glucose disappearance rate was abnormal. The results suggest that diabetes in Friedreich's ataxia is caused by a loss of islet cells similar to common Type 1 diabetes but without HLA-association and without serologic evidence for autoimmune destruction of the islet cells.