Diabetes mellitus in patients with infantile cystinosis after renal transplantation.

Diabetes mellitus is a frequent long-term complication of infantile nephropathic cystinosis. We studied 44 cystinotic patients, aged 22.1+/-5.4 years, transplanted at a mean age of 11.3+/-2.5 years; 25% were treated with insulin at 20 years of age or 10 years after transplantation, and over half required insulin at latest follow-up. In comparison, diabetes mellitus occurred in only 1% of non-cystinotic transplanted patients. Sequential oral glucose tolerance tests (OGTTs) in these patients showed the progressive deterioration of glucose metabolism. All but 2 patients had an abnormal response at latest follow-up. The high doses of corticosteroid given after transplantation or during rejection episodes were responsible for transient insulin dependency. However, the development of impaired glucose tolerance and diabetes mellitus depended mainly on the cystinotic process, which developed slowly with time. The deterioration of glucose tolerance was correlated with a decreased early phase of insulin secretion, estimated from the plasma insulin level at 30 min of the OGTT, while there was no evidence of insulin resistance. The occurrence of diabetes mellitus correlated with a worsening of the vital prognosis.