Cystinic nephrolythiasis: clinical experience and new diagnostic and therapeutic perspectives

Cystinuria is an inherited autosomal recessive disease with a prevalence 1:7000 and typical age of onset in the second decade of life. This nephrolithiasis is not always well known and well studied and for this reason it is often underdiagnosed. Cystinuria is characterized by increased urinary excretion of cystine and dibasic amino acids (lysine, ornithine, arginine) caused by defective transport of these amino acids across the luminal membrane of proximal tubule and small intestine cells. Two mutated genes responsible of this tubular defect are SLC3A1 on chromosome 2 and SLC7A9 on chromosome 19. Clinical manifestations of cystinuria are essentially those related to stones formation and their movement across the urinary tract, like flank pain/abdomen pain and hematuria, as occurred in other nephrolithiasis types. Diagnosis is based on biochemical urine analysis, stone analysis and imaging. Genetic study of this disease may be a new and stimulating approach to better understand the defects and identify new therapeutic targets. A wider knowledge and a more detailed approach to cystinuria may help to ameliorate patients quality of life, to prevent recurrences and complications and to develop more specific and adequate treatments.