The Complexity of Genotype‐Phenotype Correlations in Hereditary Spherocytosis: A Cohort of 95 Patients

Abstract

Hereditary spherocytosis (HS) is a phenotypically and genetically heterogeneous disease. With the increased use of Next Generation Sequencing (NGS) techniques in the diagnosis of red blood cell disorders, the list of unique pathogenic mutations underlying HS is growing rapidly. In this study, we aimed to explore genotype-phenotype correlation in 95 HS patients genotyped by targeted NGS as part of routine diagnostics (UMC Utrecht, Utrecht, The Netherlands). In 85/95 (89%) of patients a pathogenic mutation was identified, including 56 novel mutations. <i>SPTA1</i> mutations were most frequently encountered (36%, 31/85 patients), primarily in patients with autosomal recessive forms of HS. Three <i>SPTA1</i> (α-spectrin) mutations showed autosomal dominant inheritance. <i>ANK1</i> (ankyrin1) mutations accounted for 27% (23/85 patients) and <i>SPTB</i> (β-spectrin) mutations for 20% (17/85 patients). Moderate or severe HS was more frequent in patients with <i>SPTB</i> or <i>ANK1</i> mutations, reflected by lower hemoglobin concentrations and higher reticulocyte counts. Interestingly, mutations affecting spectrin association domains of <i>ANK1</i>, <i>SPTA1</i> and <i>SPTB</i> resulted in more severe phenotypes. Additionally, we observed a clear association between phenotype and aspects of red cell deformability as determined by the Laser assisted Optical Rotational Cell Analyzer (LoRRca MaxSis). Both maximal deformability and area under the curve were negatively associated with disease severity (respectively r = -0.46, p < 0.01, and r = -0.39, p = 0.01). Genotype-phenotype prediction in HS facilitates insight in consequences of pathogenic mutations for the assembly and dynamic interactions of the red cell cytoskeleton. In addition, we show that measurements of red blood cell deformability are clearly correlated with HS severity.