Citrin deficiency, autosomal recessive disorder, caused by mutation of SLC25A13 gene on chromosome 7q21.3 has two major phenotypes : neonatal intrahepatic chnlestatic hepatitis(N1CCD) and adult-onset type Ⅱ citrullinemia(CTLN2).So far, we have identified 52 SLC25A13 mutations and diagnosed the patients not only in Japan(166 CTLN2 and 238 NICCD) but also in other countries.We have detected 76 Chinese, 13 Korean and 15 Vietnamese patients with the same mutations as Japanese, and 13 patients(from Israel, UK, USA or Czech)with mutations different from those found in Japanese,indicating a wide distribution of citrin deficiency.DNA diagnoses of 13 known SLG25A13 mutations revealed that the carrier frequency was high in East Asian populations:Chinese(73/4 600=1/63) ,Japanese(21/1372=1/65) and Korean(25/2 690=1/108), suggesting that near by 100 000 East Asians are liomozygotes.It is important to find out patients with citrin deficiency,to treat them,and to prevent onset of severe CTLN2.