Progression of chronic renal failure in a historical group of patients with nephropathic cystinosis. European Collaborative Study on Cystinosis.

In a historical group of 205 patients with infantile or adolescent cystinosis treated without cysteamine, the rate of deterioration of renal function was analysed retrospectively. Patient survival curves and renal survival data are presented. Longitudinal data of serum creatinine values (n = 3280) in 157 patients were plotted for each patient, smoothed by the method of the running medians and grouped into 12 serum creatinine classes. In every patient the age at the last smoothed serum creatinine value observed in each serum creatinine class was determined. These virtual age values were then summarized per serum creatinine class, expressed as median and centiles and plotted, thus describing the "natural" course of the disease. In 9 pairs of affected siblings the rate of progression showed a median difference of about 12 months. Our data describe the "natural" course of nephropathic cystinosis and can be used as a prognostic aid for recently detected patients. The data can also be applied for the assessment of the influence of new therapeutic strategies on the rate of progression of renal failure in cystinotic patients.