A Chinese adult onset type II citrullinaemia patient with 851del4/1638ins23 mutations in the SLC25A13 gene.

Editor—Classical citrullinaemia (CTLN1) is a rare metabolic disease caused by the deficiency of argininosuccinate synthetase (ASS, E.C.6.3.4.5), which usually has its onset in neonates or young infants.1 These patients may present with acute onset of disturbance of consciousness and hyperammonaemia. ASS activity is very low in all tissues tested and over 30 mutations of the ASS gene have been identified in about 50 CTLN1 patients.2 However, in Japan, many cases with adult onset type II citrullinaemia (CTLN2) have been reported.3 A previous study in CTLN2 showed a specific deficiency of ASS protein in the liver, but no ASS gene mutation could be found.4 Recently, the gene responsible for CTLN2 was identified by homozygosity mapping.5 This gene, SLC25A13 , encodes a putative calcium dependent mitochondrial carrier protein (called citrin). A loss of organisation caused by the absence of functional citrin has been proposed to lead to the reduction of ASS protein in the liver. In this report, we present a Chinese patient with CTLN2. She was well until 40 years …