The mRNA levels of the Cl− extrusion system (KCC2) and the Cl− intrusion system (NKCC1) were detected by real-time RT-PCR in the plasma of 29 cirrhotic patients with HE of grade I-II, 36 cirrhotic patients with HE of grade III–IV, 20 cirrhotic patients without HE and 15 healthy controls. The gene discussed is SLC12A2; the disease is hereditary elliptocytosis.