Chromosome 22 is an acrocentric chromosome containing 500-600 genes, representing 1.5%-2% of the total DNA in cells. It was the first human chromosome to be fully sequenced by the Human Genome Project. Several syndromes involving the partial deletion or duplication of chromosome 22 are well descibed, including 22q11.2 deletion syndrome, 22q11.2 duplication syndrome, 22q11.2 distal deletion syndrome, Phelan-McDermid syndrome caused by a 22q13 deletion or pathogenic variant in SHANK3, and cat-eye syndrome caused by a 22 pter-q11 duplication. This review aims to provide concise information on the clinical characteristics of these syndromes. In particular, the similarities in features among these syndromes, genetic basis, and standard detection techniques are described, providing guidance for diagnosis and genetic counselling.

Background: ABO typing is crucial for ensuring safe blood transfusion and is commonly performed by examining antigen-antibody interactions. Determining ABO blood group can be difficult when dealing with ABO discrepancy and ABO subgroups. ABO genotyping may be necessary to resolve ABO discrepancy. ABO genotyping primarily involves direct sequencing, with the possibility of using other molecular methods. Methods: PCR and direct sequencing of exons 6 and 7 were performed for total 108 samples from June 2010 to December 2019. Also, other molecular methods including cloning sequencing and short tandem repeat analysis were carried out just in case. Sequencing data were compared with allele information of blood group antigen mutation databases. Results: The predominant causal allele among 108 ABO discrepant cases was cis-AB01, with 28 cases. This was followed by rare ABO alleles (B309, B306, A204, Bw29, and Ax01) with 14 cases, and blood chimera with 5 cases. Five new alleles were identified during the investigation. Conclusion: This study reaffirms that cis-AB is the most common cause of inherited ABO discrepancies, and cis-AB01 is the most prevalent cis-AB allele in the Korean population, also in the southeastern region. In addition, we discovered five new alleles and five blood chimeras by adopting sequencing analysis and additional molecular techniques to resolve ABO discrepancies, which provide regional data on rare alleles. This study presents rare and new ABO alleles and blood chimeras identified over a ten-year period at two major university hospitals in Southeastern Korea.