[A Case of Okur-Chung Syndrome Caused by CSNK2A1 Gene Variation and Review of Literature]

To summarize the clinical features and gene variation characteristics of a child with Okur-Chung syndrome caused by CSNK2A1 gene variation. The medical records of one patient who was diagnosed with Okur-Chung syndrome in Department of Pediatrics, Xiangya Hospital of Central South University in July 2018 were analyzed. Using "CSNK2A1" gene as the keyword, relevant information about CSNK2A1 gene was searched at CNKI, Wangfang Data, OMIM, PubMed, ClinVar, Decipher (until August 2018). The characteristics of CSNK2A1 gene variation and the clinical phenotype of children with Okur-Chung syndrome were summarized. The boy, 1 year and 8 months old, was sent to hospital at the age of 1 year and 6 months because of delayed growth for more than 1 year. He was susceptible to cough while eating or drinking. He was also suffering from constipation and poor sleep. Physical examination showed that his body weight was 10.2 kg, microcephalus, broad nasal bridge, micrognathia and hypotonia were observed. Whole exome-sequencing test identified a heterozygous variation c.524A>G (p.D175G) in CSNK2A1 gene. This was the first case report of CSNK2A1 gene variation in the mainland of China. So far, a total of 52 cases were reported worldwide (52 single nucleotide variants), including 35 cases in 7 articles, 9 cases in Decipher database and 14 cases in ClinVar database, 6 of which were also reported in PubMed. In previously reported 52 cases, there were 48 missense variants, whereas, splice and frameshift variations were found in 3 cases and 1 case, respectively. Among the variation sites, p.K198R was the most common sites (12 cases), followed by p.R47 (6 cases), p.R80H (4 cases) and p.S51 (4 cases). Among these 52 cases, only 27 cases have been elaborately described in other studies, so the clinical characteristics were summarized in 28 cases eventually (including 27 cases in the articles and this patient), 27 of whom presented severe intellectual disability or global development delay, 1 case with mild language development delay, and 19 had hypotonia; 8 had autism spectrum disorders, 5 had attention deficit hyperactivity disorder, and 9 had sleep problems. 20 had dysmorphic facial features, 10 of them had microcephalus. 16 had failure to thrive or short stature, 12 had gastrointestinal or oromotor problem, 5 had immunological problem, and 4 had skin abnormalities. The main clinical feature of patients with CSNK2A1 gene variations is intellectual disability with multiple systems involved, such as microcephalus, abnormal facial shape and hypotonia. The variation of CSNK2A1 gene is the cause of Okur-Chung syndrome. Missense variation is the main cause, and P. K198R is the hotspot variation.