ORIGINAL ARTICLE Cystinuria in children and young adults: success of monitoring free-cystine urine levels Luca Dello Strologo & Chiara Laurenzi & Antonia Legato & Anna Pastore Received: 1 May 2007 / Revised: 4 July 2007 / Accepted: 5 July 2007 / Published online: 11 August 2007 # IPNA 2007 Abstract Medical treatment of cystinuria is often disap- pointing. Patients undergo frequent surgery, which is often followed by early relapse. The aim of our study was to evaluate the efficacy of medical treatment of cystinuria, to prevent formation or to reduce the numbers and dimensions of renal stones. Twenty cystinuric patients were treated with a combined approach, including cystine-binding drugs. Free and bound urine cystine levels were measured every 4 months. Drug dosage was adjusted to maintain free urine cystine level below 100 μmol/mmol creatinine. Eighteen patients completed the study; detection of new stones was reduced from 0.28 per year to 0.03 per year, and, in six patients, the numbers and dimensions of pre-existing renal stones were reduced. Surgery was required in one subject, and no relapse was observed 12 months afterwards. The dosage required to achieve target levels was closely correlated with patient body weight: older children required a lower dose. Medical management of cystinuria is feasible. The treatment must be personalised in children, as the amount of drug required is strictly dependent on body size. Keywords Cystinuria . Medical treatment . Cystine-binding drugs . Children . Renal stones Introduction Cystinuria is an autosomal recessive disorder characterised by impaired handling of cystine and dibasic amino acids by the renal proximal tubules and intestines [1]. Its main clinical feature is the recurrence of renal stones. A combined medical approach is commonly used to treat this disorder, but its efficacy is still controversial [2] and surgery is frequently required to remove urinary stones. Unfortu- nately, there is a high incidence of early relapse after surgical intervention [3], most likely due to insufficient preventive therapy. The aim of our study was to evaluate prospectively, in a paediatric population, the efficacy of a medical approach for long-term treatment of cystinuria, to prevent the formation of new renal stones and to reduce the numbers and dimensions of pre-existing renal stones. Material and methods Cystinuria was arbitrarily defined as cystine excretion above 300 μmol/mmol of creatinine in patients with a history of at least one cystine renal stone. Twenty patients with proven cystinuria, who had had at least one renal stone at the start of the study or in whom a renal stone had previously been removed by surgery or percutaneous lithotripsy, were included in the study. Two of the 20 patients were excluded from the study in the first 2 months due to allergy to penicillamine and mercaptopropionyl glycine (tiopronin), in one case, and to the development of severe proteinuria in the other. These patients were excluded from all evaluations. A third patient developed proteinuria 60 months after starting treatment, and mercaptopropionyl glycine was with- Pediatr Nephrol (2007) 22:1869–1873 DOI 10.1007/s00467-007-0575-2 L. Dello Strologo (*) : C. Laurenzi : A. Legato Nephrology and Urology Department, Bambino Gesù Children’ s Hospital and Research Institute, Piazza S. Onofrio 4, 00165 Rome, Italy e-mail: dellostrologo@opbg.net A. Pastore Clinical Biochemistry Unit, Bambino Gesù Children’ s Research Hospital, Rome, Italy