Delineation of cystinuria in Saudi Arabia: A case series.
Cystinuria is an inherited metabolic disease that is caused by defects in two genes, SLC3A1 and SLC7A9, which result in a renal reabsorptive defect of cystine and other dibasic amino acids, including ornithine, arginine, and lysine. Patients usually present with recurrent renal calculi and may develop renal impairment. Medical management includes high fluid intake and chelating agents. To the best of our knowledge, this is the first study describing cystinuria in Saudi Arabia.



A retrospective chart review for cystinuria patients from the genetic and nephrology divisions between 2010 to 2015. All patients were investigated, diagnosed and treated at King Abdulaziz Medical City in Saudi Arabia.



Eight patients were identified from five unrelated families. The age of onset ranged from birth to 14 years. The female to male ratio was 1.7:1. Two new variants in the SLC3A1 and SLC9A7 genes were discovered. All of the detected mutations were missense variants in three different exons, such as c.1711 T > A (p.Cys571Ser) (exon 10), c.1166C > T p.Thr389Met (exon 11) and c.1400 T > A p.Met467Lys (exon 8). Additionally, 37.5% of our patients developed arterial hypertension and 25% had urinary tract infection, but none had renal impairment. No significant clinical differences were detected in this study between type A (SLC3A1 variants) and type B cystinuria (SLC7A9 variant). Two cases were diagnosed based on clinical information, biochemical testing and a positive family history as all of the molecular testing for cystinuria was negative.



Cystinuria has wide genetic heterogeneity with a poor genotype/phenotype correlation. Negative molecular investigations should not rule out the disease if clinical and biochemical investigations support the diagnosis. A larger data registry is essential to better describe the cystinuria genotype/phenotype in Saudi Arabia.
King Abdullah International Medical Research Centre, King Saud bin Abdulaziz University for Health Sciences, Genetic Division, Department of Pediatrics, King Abdulaziz Medical City, Ministry of National Guard-Health Affairs (NGHA), PO Box 22490, Riyadh, 11426, Saudi Arabia.
Abdulrahman
A
Obaid
King Abdullah International Medical Research Centre, King Saud bin Abdulaziz University for Health Sciences, Genetic Division, Department of Pediatrics, King Abdulaziz Medical City, Ministry of National Guard-Health Affairs (NGHA), PO Box 22490, Riyadh, 11426, Saudi Arabia.
Marwan
M
Nashabat
King Abdullah International Medical Research Centre, King Saud bin Abdulaziz University for Health Sciences, Nephrology Division, Department of Pediatrics, King Abdulaziz Medical City, Ministry of National Guard-Health Affairs (NGHA), PO Box 22490, Riyadh, 11426, Saudi Arabia.
Khalid
K
Al Fakeeh
King Abdullah International Medical Research Centre, King Saud bin Abdulaziz University for Health Sciences, Nephrology Division, Department of Pediatrics, King Abdulaziz Medical City, Ministry of National Guard-Health Affairs (NGHA), PO Box 22490, Riyadh, 11426, Saudi Arabia.
Abdullah T
AT
Al Qahtani
King Abdullah International Medical Research Centre, King Saud bin Abdulaziz University for Health Sciences, Genetic Division, Department of Pediatrics, King Abdulaziz Medical City, Ministry of National Guard-Health Affairs (NGHA), PO Box 22490, Riyadh, 11426, Saudi Arabia. dralfadhelm@gmail.com.
Majid
M
Alfadhel
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D026923:Amino Acid Transport Systems, Basic / Q000235:genetics*; D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics*; D002648:Child; D003555:Cystinuria / Q000150:complications / Q000235:genetics*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000209:etiology; D008297:Male; D020125:Mutation, Missense; D012189:Retrospective Studies; D012529:Saudi Arabia; D014552:Urinary Tract Infections / Q000209:etiology; D055815:Young Adult
D026923:Amino Acid Transport Systems, Basic; D026921:Amino Acid Transport Systems, Neutral; C489857:SLC3A1 protein, human; C499489:SLC7A9 protein, human
Cystinuria; Renal calculi; SLC3A1; SLC7A9