Receiver operating characteristic curve analyses revealed that a body mass index < 20kg/m(2) and serum PSTI>29ng/mL were associated with citrin deficiency.
The patient complained of anorexia, lethargy, fatigue and poor growth, and showed laboratory findings typical of CTLN2; elevated levels of plasma citrulline, threonine-to-serine ratio, and serum pancreatic secretory trypsin inhibitor.
The diagnosis of CTLN2 was confirmed by elevations of plasma citrulline level (384.3 nmol/mL; normal 17-43 nmol/mL) and serum pancreatic secretory trypsin inhibitor (PSTI) (110 ng/mL; normal 4.6-12.2 ng/mL), decrease in hepatic argininosuccinate synthetase activity (5.5% of control), lack of hepatic citrin protein expression and mutations in SLC25A13 gene (compound heterozygote with S225X and Ex1-1G>A).