Citrin deficiency: an infant incidentally detected by phenylketonuria screening with a novel mutation in SLC25A13 gene: We report the first Turkish patient with citrin deficiency detected incidentally by phenylketonuria screening. Mild cholestasis, increased a-fetoprotein level, aminoacidemia including citrulline and coagulation disorder suggested citrin deficiency. Screening the SLC25A13 gene revealed compound heterozygosity harboring a novel mutation, c.851-854de1GTAT (p.M285Pfs*2)/ p.I290T (c.869T>C). Progression to type II citrullinemia was considered due to hyperammonemia episodes resulting from high carbohydrate/low protein diet. High protein/low carbohydrate diet resulted in cessation of hyperammonemia episodes, reversal of hepatic dysfunction and steatohepatitis. Our report illustrates the importance of awareness on citrin deficiency.