Unlike GS, which originates from inactivating mutations in the SLC12A3 gene, BS primarily stems from 5 known gene defects: SLC12A1, KCNJ1, CLCNKB, BSND/CLCNKA/CLCNKB, and CaSR.[18–20] Accurate identification of these genetic defects is paramount for diagnosis. The gene discussed is CLCNKB; the disease is Bloom syndrome.