Cystic kidney disease in a patient with systemic toxicity from long-term D-penicillamine use

Mass Spectrometry-based in vitro Assay to Identify Drugs that Influence Cystine Solubility

Cystinuria is a rare genetic disorder characterized by recurrent, painful kidney stones, primarily composed of cystine, the dimer of the amino acid cysteine (Sumorok and Goldfarb, 2013). Using a mouse model of cystinuria, we have recently shown that administration of drugs that increase cystine solubility in the urine can be a novel therapeutic strategy for the clinical management of the disease (Zee et al., 2017). There is a large unmet need in the field for developing new drugs for cystinuria. To that end, here we describe a simple in vitro cystine solubility assay that is amenable for screening compounds to identify potential drugs that may influence cystine solubility. The assay includes preparing a supersaturated solution of cystine, incubating this solution with drug(s) of choice, and finally using high pressure liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to quantify the amount of cystine precipitated under various conditions.

Case Report: Cystinuria and Polycystic Kidney Disease

Cystinuria and polycystic kidney disease are 2 genetic disorders that affect the genitourinary tract but rarely together. This case report presents 2 pediatric patients diagnosed with polycystic kidney disease and cystinuria requiring surgical treatment. Both subjects presented acutely with stone disease. Imaging studies and stone analysis established the diagnoses. Although coexistence of these 2 conditions is rare, cystinuria should be considered in the differential diagnosis when evaluating patients with cystic disease who develop renal calculi.