rs59172778

rs59172778, also known as c.1013T>C or p.Met338Thr, is a relatively rare variant in the KCNJ1 gene. The minor rs59172778(G) allele was originally reported (in 1996) as a mutation leading to recessively inherited type 2 Bartter syndrome. The (G) allele is rare, usually being found in just under 1% of allele counts, but Bartter syndrome appears to be even rarer. This implies that the (G) allele may not be fully causative or penetrant, and more recently (as of ~2015) two labs are reporting in ClinVar that they believe this variant is benign. Anecdotally, we (SNPedia) have also heard from an rs59172778(G;G) individual who has no signs of Bartter syndrome. So while it remains possible that the rs59172778(G) allele is a very weakly penetrant mutation associated with Bartter syndrome as originally reported, the preponderance of evidence is now indicating it is a benign polymorphism.