MEN (General Swiss-German Mennonite)

Inheritance: autosomal recessive
Genes: SLC3A1

CSNU
Cystinuria type I
Cystinuria type II
Cystinuria type III

Kidney stones

Kidney failure

Urinary obstruction

Urinary infections

Cystinuria

Clinical Characteristics

General description (for patients):

This is one of the more common inherited amino acid disorders.  It results from a defect in kidney function that manifests itself through the formation of kidney and bladder stones.  These can lead to obstruction of urine flow that raises the risk of urinary infections and kidney failure.

Medical description:  

Cystinuria results from defective transport of cystine and dibasic amino acids through the epithelial cells of the renal tubule and intestinal tract.  The low solubility of cystine leads to the formation of stones in the urinary tract with the usual secondary complications which can result in end stage kidney disease.  Several subtypes have been distinguished with variable urinary amino acid excretion profiles.  Heterozygotes (carriers) may also have an increased risk of urinary tract stone formation.

Genetics:

The mutations causing cystinuria can be in the SLC3A1 gene located on chromosome 2 (2p15.3) or in the SLC7A9 gene on chromosome 19 (19q13.1).  The two gene products comprise a multi-unit complex (active in amino acid transport) in which multiple mutations have been described.   At least four mutations occur in the Old Order Mennonites in Pennsylvania: two in the heavy subunit encoded by the SLC3A1 gene as well as two mutations in the lighter subunit.  Cystinuria is an autosomal recessive disorder but heterozygotes with types II and III can have abnormal urinary excretion patterns (elevated levels of cystine and lysine) and an increased risk of stone formation.

Treatment:

Treatment is directed at prevention of stone formation through high fluid intake and the use of penicillamine.

Prognosis:

Depends upon prompt diagnosis and prevention of urinary obstructions.

Ancillary treatments and support:


Specialists and specialty centers:

Nephrologist, internist, nutritionist.

References:

Endsley, J.K., Phillips, J.A. III, Hruska, K.A., Denneberg, T., Carlson, J., and George, A.L., Jr.:  Genomic organization of a human cystine transporter gene (SLC3A1) and identification of novel mutations causing cystinuria.  Kidney Int. 51: 1893-1899, 1997.  PubMed ID: 9186880

Font-Llitjos, M., Jimez-Vidal, M., Bisceglia, L., Di Perna, M., de Sanctis, L., Rousand, F., Zelante, L., Palacin, M., and Nunes, V.:  New insights into cystinuria: 40 new mutations, genotype-phenotype correlation, and digenic inheritance causing partial phenotype.  J. Med. Genet. 42: 58-68, 2005.  PubMed ID: 15635077

Resources:

National Kidney Foundation
Cystinuria Support Network

Associated Graphics