Phenotypical traits in cystinuria: a study of 20 families in the ComunidadValenciana (Spain)

BACKGROUND: The aim of this study was to classify phenotypically cystinuria patients in the Comunidad Valenciana using their genealogy and to study th e large heterogeneity of the disease expression. SUBJECTS AND METHOD: From 29 patients diagnosed of cystinuria, 20 families were enrolled in the study. An urine sample of every subject was collected to quantify urine aminoacides using high pressure liquid chromatography. We also looked for the presence of cystine crystals. Genetic analyses were ca rried out using PCR (Polymerase Chain Reaction), and RFLPs (Restriction Fra gment Length Polymorphisms). Demographic and clinical characteristics were recorded in a standard questionnaire. RESULTS: From 20 families, 4 were classified Type I, 10 as Type non I, and 6 as Type unknown. Type I cystinuria patients showed the highest urinary le vels of cystine and ornithine. We also found an association of cystine crys tals and M467T mutation in SLC3A1 gene with Type I. However, we did not fin d a higher risk of nephrolithiasis associated to any family type. CONCLUSIONS: Phenotypical characterization of patients with cystinuria has showed the wide variability of phenotypical traits indeed in the same trans mission pattern. This variability could be due to the genetic and environme ntal heterogeneity which has developed this pathology and modulated its evo lution.