Hereditary spherocytosis caused by copy number variation in SPTB gene identified through targeted next-generation sequencing.

Hereditary spherocytosis (HS) is a heterogeneous genetic disorder characterized by spherocytosis on peripheral blood smear with hemolytic anemia, accompanied by signs of hemolysis. Herein, we report a 5-month-old Korean girl with HS resulting from a de novo 271 Kb microdeletion of 14q23.3. She presented with hemolytic anemia and mild splenomegaly. Spherocytosis was seen on examination of peripheral blood. Eosin-5'-maleimide (EMA) test and flow cytometric osmotic fragility test were positive. She had no relevant family history of spherocytosis. No pathogenic single nucleotide variants or small insertions/deletions were detected in HS-associated genes. Array comparative genomic hybridization analysis revealed a 271 Kb deletion at chromosome 14q23.3, encompassing the SPTB, CHURC1, GPX2, RAB15, FNTB, and MAX genes. We found a deletion affecting 5' UTR, exon 1, and part of intron 1 of the SPTB gene using targeted next-generation sequencing (NGS) analysis, suggesting that NGS may be able to identify disease-causing copy number variations (CNVs), as well as small point mutations in HS patients. In addition, chromosomal microarray may be useful in defining combined deleted genes. Additional evaluations should thus be considered in the diagnosis of HS, especially when CNV is revealed as disease-causing abnormality.