Objectives Urea cycle disorders (UCDs) are rare hereditary diseases. This study was conducted to help identify the characteristics of UCDs in Turkey. Methods The primary outcome was to determine patient characteristics. Investigating the relationships between the patient outcomes and ammonia levels were the secondary outcomes. Eighty five patients from 79 families, diagnosed with UCD at a single metabolic referral center between 1979 and 2017, were included. Clinical and laboratory data were retrieved retrospectively from hospital records. Results Classical citrullinemia was the most common type of UCD; citrin deficiency and carbamoyl phosphate synthase 1 deficiency (CPS1D) were the rarest. One thirty one hyperammonemic episodes were recorded. The peak ammonia levels were found to be significantly associated with polycythemia and hypocalcemia at presentation. The median peak ammonia values of the patients who died were higher than those of the survivors. The highest mortality rate was in the classical citrullinemia group. The mortality rate of the first hyperammonemic crisis was 28.6%, while it was 6.7% in subsequent episodes with an odds ratio of 4.28 (95% CI: 1.67-11.0) (p=0.001). Forty-four patients underwent genetic analysis and genetic variants were detected in 42 patients (95%). Three of the detected variants have not been previously reported. Conclusions This is the largest UCD series in Turkey and may serve as a guide to clinical, biochemical and genetic features of UCDs in our country. Prevention of hyperammonemia may be the most influential measure to improve long term survival.
Keywords: genetic diseases; hyperammonemia; inborn errors of metabolism; urea cycle disorders.