Understanding the genetic architecture and phenotypic landscape of SPTB gene variants causing hereditary spherocytosis in an Indian cohort.

Hereditary spherocytosis (HS) is a common form of haemolytic anaemia caused by defects or deficiencies in genes encoding erythrocyte membrane proteins, such as ANK1, SPTB, SLC4A1, EPB42, and SPTA1. Among these, ANK1 and SPTB mutations are the most frequent causes of HS worldwide. This study analysed 53 Indian HS patients, identifying 33 novel and 12 previously reported SPTB variants using targeted next-generation sequencing (t-NGS). The identified SPTB variants included frameshift (28%), missense (24%), nonsense (44%), and splicing (4%) types, with nonsense variants being the most common. These nonsense variants typically result in truncated proteins. The variants were widely distributed across the gene, with the highest density observed in the spectrin repeats and ankyrin-binding domain, while no variants were found in the tetramerization domain. All identified SPTB variants exhibited heterozygous inheritance, consistent with an autosomal dominant inheritance pattern of the gene causing HS. One patient, however, carried compound heterozygous variants, leading to severe anaemia, and five patients had de novo SPTB variants. This study expands the spectrum of SPTB variants, enhances the understanding of spectrin-related molecular defects, establishes genotype-phenotype correlations, and provides valuable insights for laboratories developing genetic tests for HS. The high number of identified variants highlights the importance of advanced technologies like NGS for accurate molecular diagnosis in HS disorder. This approach not only supports clinical diagnostics but also aids in family counseling for improved management of HS.