Hereditary elliptocytosis (HE) is a hereditary hemolytic anemia characterized by an increased number of elliptocytes in the peripheral blood. It's caused by mutations in genes encoding red blood cell membrane or skeletal proteins, leading to abnormal red blood cell membranes. The disease is primarily inherited as an autosomal dominant trait and mainly involves the SPTA1, SPTB, and EPB41 genes, which code for α-spectrin, β-spectrin, and band 4.1 protein respectively. The prevalence of HE varies globally, ranging from 0.03%–0.05% in Europe and America to 0.6%–1.6% in malaria-endemic regions of Africa. The literature primarily consists of scattered case reports or family studies. Many HE patients are asymptomatic and easily confused with hereditary spherocytosis. Understanding the genetic mutation characteristics of HE and the relationship between genotype and clinical phenotype is crucial for accurate diagnosis. This study aims to report on 9 confirmed cases of HE, summarizing the genetic mutation characteristics to improve diagnostic accuracy.

Existing literature on HE predominantly comprises individual case reports or family-based studies, often lacking a comprehensive overview of genetic mutations and their correlation with clinical manifestations. Studies have highlighted the involvement of SPTA1, SPTB, and EPB41 genes, with SPTA1 being the most frequently mutated. Specific mutations within these genes, particularly in SPTA1's 2nd exon (e.g., c.82C>T, p.R28C and c.83G>A, p.R28H), are frequently reported. The severity of the disease appears to vary significantly, even within families carrying the same mutation, suggesting modifying factors influence the clinical outcome. The literature also mentions the connection between the degree of 4.1R protein deficiency (caused by EPB41 mutations) and the clinical severity. A complete deficiency correlates with severe anemia, while partial deficiency can result in mild HE with minimal or no hemolysis. Information regarding SPTB mutations and their clinical correlation is limited due to fewer reported cases. This study aims to add to the existing literature by providing a detailed analysis of nine cases and reviewing the current understanding of HE's genetic and clinical landscape.

This retrospective study included 9 HE patients from 8 independent families diagnosed between June 2018 and February 2022 at the Anemia Diagnosis and Treatment Center of the Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences. Diagnosis was confirmed using detailed history taking, physical examination, laboratory tests, and imaging studies, adhering to established criteria. Laboratory tests encompassed complete blood counts, peripheral blood smears, free hemoglobin (F-HB), haptoglobin (HP), red blood cell lifespan determination (endogenous CO breath test), red blood cell membrane disease-related hemolysis tests (osmotic fragility test, acidified glycerol lysis test, eosin-5'-maleimide test), red blood cell enzymeopathy-related hemolysis tests (glucose-6-phosphate dehydrogenase, pyruvate kinase, red blood cell pyrimidine 5'-nucleotidase), hemoglobinopathy-related hemolysis tests (HbA2, HbF), acquired hemolytic anemia tests (direct Coombs test, acid hemolysis test, cold agglutinin test), and digestive system ultrasound. Next-generation sequencing (NGS) was performed to identify gene mutations, with an average sequencing coverage of 99.59% and an average sequencing depth of 569.67×. Sequencing results were compared with the Human Gene Mutation Database (HGMD) and the 1000 Genomes database. Pathogenicity analysis was conducted according to the ACMG guidelines, integrating clinical characteristics and family history. Sanger sequencing validated mutation sites in patients and their parents.

Nine patients (3 male, 6 female; median age 40 years) were included. Eight patients had splenomegaly, five had jaundice, four had fatigue, three had dark urine, and two had intermittent fever. Six patients had a family history of anemia. Eight of the nine patients showed mild to moderate anemia (median hemoglobin 84 g/L). NGS identified mutations in SPTA1 (6 cases: 3 single heterozygous, 2 compound heterozygous, 1 deletion), SPTB (1 case), and EPB41 (1 case), totaling 11 mutation sites. Mutations in SPTA1 were found in exons 2, 6–12, 9, 15, and 44. The SPTB mutation was located in exon 2, and the EPB41 mutation in exon 17. Three patients carried mutations in exon 9 of the SPTA1 gene, showing varying degrees of anemia. Family history confirmed the inheritance pattern in three cases. The most common mutations were in the SPTA1 gene, especially at codon 28. Mutations in the SPTA1 gene, notably at codon 28, are highlighted as frequent occurrences, consistent with existing literature. Variability in clinical presentation was observed even with identical mutations, emphasizing the role of modifying factors. One patient demonstrated a 20q chromosome deletion, a finding previously reported in myelodysplastic syndrome (MDS) patients with acquired elliptocytosis.

This study confirms the significant role of SPTA1, SPTB, and EPB41 genes in HE pathogenesis, aligning with previous research. The frequent mutations at codon 28 of SPTA1 highlight its importance in red blood cell structure and function. The observed phenotypic variability among individuals with the same mutation underscores the influence of modifying factors and the complexity of HE's genotype-phenotype correlation. The detection of 20q chromosome deletion in one patient further demonstrates the diversity of genetic events contributing to this condition. The limitations of the study, such as the relative small sample size and potential for underreporting of asymptomatic cases, highlight the need for larger scale studies to more accurately define genotype-phenotype correlations in HE.

This study expands the understanding of HE by characterizing nine cases with diverse genetic mutations affecting SPTA1, SPTB, and EPB41 genes. The findings emphasize the importance of comprehensive genetic testing for accurate diagnosis and improved management of HE patients. Future research with larger, more diverse cohorts is necessary to further refine genotype-phenotype correlations and to uncover additional contributing genetic factors.

The retrospective nature of the study and relatively small sample size limit the generalizability of the findings. The possibility of asymptomatic HE cases remaining undiagnosed introduces a selection bias. Further research with a larger and more geographically diverse sample size is needed to fully elucidate the relationship between genotype and phenotype in HE. Additionally, functional studies are necessary to further understand the impact of these mutations on protein function.