BS is currently classified into five different subtypes according to the gene mutations involved: mutation of SLC12A1 (Na-K-2Cl cotransporter (NKCC2)) causes type I BS [4], mutation of KCNJ1 (ATP-Regulated Potassium Channel (ROMK)) causes type II BS [4], mutation of CLCNKB (Chloride channel Kb (CLCNKB)) causes type III BS [5], mutation of BSND (chloride channel protein ClC-Ka (CLCNKA) and subunit of ClC-Kb (BRTTIN)) causes type IV-A BS [6], mutation of CLCNKB and CLCNKA cause type IV-B BS [7], and mutation of CASR (Calcium-Sensing Receptor) causes type V BS [8]. The gene discussed is KCNJ1; the disease is Bloom syndrome.