A novel variant mutation for congenital dyserythropoietic anemia, type II

Identification of a Novel Mutation in the SEC23B Gene Associated With Congenital Dyserythropoietic Anemia Type II Through the Use of Next-generation Sequencing Panel in an Undiagnosed Case of Nonimmune Hereditary Hemolytic Anemia

Congenital dyserythropoietic anemias (CDAs) are rare hereditary blood disorders characterized by ineffective erythropoiesis, hemolysis, and erythroblast morphologic abnormalities in the bone marrow. The 3 main types of CDA, I to III, and variant types of CDA, IV-VIII, have been described. The causative genes have been identified as CDAN1, C15ORF41, SEC23B, KIF23, KLF1, and GATA1. CDA type II is the most frequent form. Typical symptoms are jaundice, hepatosplenomegaly, mild-to-severe normocytic anemia, and inadequate reticulocyte response. We report an 18-year-old boy who had chronic mild congenital anemia, jaundice, and splenomegaly mimicking nonautoimmune hemolytic anemia since 18 months of age. Compound heterozygous mutations in SEC23B gene were detected by the use of a gene-targeted next-generation sequencing panel: the already reported missense mutation c.40C>T (p.Arg14Trp), and a new frameshift deletion (c.489_489delG, p.Val164Trpfs*3), confirming the diagnosis of CDA type II. The study underlines the molecular heterogeneity of CDA II and the importance of a precise diagnosis in rare congenital diseases such as CDA II. In consequence, it can be difficult to diagnose because of limited resources, financial constraint, and rarity of disease in the developing country. Advanced laboratories and new molecular approaches may help in diagnosing rare anemias.

Analysis of a cohort of 101 CDAII patients: description of 24 new molecular variants and genotype-phenotype correlations

Congenital dyserythropoietic anaemia type II (CDAII) is a rare autosomal recessive disease characterized by ineffective erythropoiesis, haemolysis, erythroblast morphological abnormalities, hypoglycosylation of some red blood cell membrane proteins, particularly band 3, and mutations in the SEC23B gene. We report the analysis of 101 patients from 91 families with a median follow-up of 23 years (range 0-65); 68 patients are newly reported. Clinical and haematological parameters were separately analysed in early infancy and thereafter, when feasible. Molecular analysis of the SEC23B gene confirmed the high heterogeneity of the defect, leading to the identification of 54 different mutations, 24 of which are newly described. To evaluate the genotype-phenotype correlation, patients were grouped according to their genotype (two missense mutations vs. one missense/one drastic mutation) and assigned to two different severity gradings based on laboratory data and on therapeutic needs; by this approach only a weak genotype-phenotype correlation was observed in the analysed groups.

Retrospective cohort study of 205 cases with congenital dyserythropoietic anemia type II: definition of clinical and molecular spectrum and identification of new diagnostic scores

Congenital Dyserythropoietic Anemia II (CDA II) is a rare hyporegenerative anemia of variable degree, whose causative gene is SEC23B. More than 60 causative mutations in 142 independent pedigrees have been described so far. However, the prevalence of the CDA II is probably underestimated, since its clinical spectrum was not yet well-defined and thus it is often misdiagnosed with more frequent clinically-related anemias. This study represents the first meta-analysis on clinical and molecular spectrum of CDA II from the largest cohort of cases ever described. We characterized 41 new cases and 18 mutations not yet associated to CDA II, thus expanding the global series to 205 cases (172 unrelated) and the total number of causative variants to 84. The 68.3% of patients are included in our International Registry of CDA II (Napoli, Italy). A genotype-phenotype correlation in three genotypic groups of patients was assessed. To quantify the degree of severity in each patient, a method based on ranking score was performed. We introduced a clinical index to easily discriminate patients with a well-compensated hemolytic anemia from those with ineffective erythropoiesis. Finally, the worldwide geographical distribution of SEC23B alleles highlighted the presence of multiple founder effects in different areas of the world.