To explore the clinical characteristics of a late-onset ornithine carbamoyltransferase deficiency (OTCD) child, and analyze OTCD by summarizing pertinent literatures.

A 10-month old male child complained with ＂intermittence vomit 7 d, twitched 1 d＂ who was diagnosed as OTCD and rescued in Department of Intensive Care Unit in Nanjing Children′s Hospital on 13 September 2015, was chosen as study subject. The clinical data of the OTCD child was analyzed by retrospective method, including the results of tandem mass spectrometry (MS/MS) detection after born, clinical manifestations, laboratory examination results and therapy. The cases of OTCD were searched from Wanfang, CNKI and PubMed database, and the clinical characteristics of OTCD were summarized.

① The case report results were as follows. In this case, routine MS/MS screening was performed in 72 h after birth and the result showed the concentration of citrulline was normal. The child presented with vomiting, lethargy and twitch at the age of 10 months, blood ammonia was over 200 μmol/L, no obvious abnormality was detected of the MS/MS, and his urine gas chromatography-mass spectrometry (GC/MS) revealed a large number of orotic acid and urine uracil. A novel compound mutation of the ornithine carbamoyltransferase (OTC) gene c. 386G>A(p.Arg129His) was identified in the child by Ion Torrent semiconductor sequencing technology. His mother was found of heterozygous with c. 386G>A(p.Arg129His) mutation. Low protein diet was provided for the child and ammonia scavenger treatment were conducted consist of arginine and sodium benzoate. The child died on the 20th day after admission after his family members abandoned treatment for poor treatment effect. ② Literature retrieval results were as follows. A total of 10 related domestic literatures of OTCD with relatively complete clinical data were searched and a total of 12 OTCD patients were included, besides, 5 related literatures from abroad of OTCD with relatively complete clinical data were searched and a total of 5 OTCD patients were included. According to the analysis results of literatures, the main clinical manifestations of OTCD were nonspecific digestive tract and nervous system symptoms, 41.2% (7/17) of OTCD patients had decreased concentration of citrulline in their blood sample, and 94.1% (16/17) of OTCD patients had increased concentration of orotic acid and urine uracil in their urine sample. Mutation sites of OTC gene were detected by gene testing in 35.3%(6/17) patients, the mortality rate of OTCD was high, and the prognosis was poor.

Clinical manifestations of OTCD are not specific, and the diagnosis of OTCD is relied on MS/MS and urine GC/MC detection, and the diagnose golden standard of gene diagnosis. The mortality of OTCD is high and its prognosis is poor. There is no practicable systematic treatment project for OTCD until now, so it is necessary for clinicians to improve the knowledge and the level of diagnosis and treatment of OTCD.