Aplastic crisis as a complication of congenital dyserythropoietic anemia type II

New Cases and Mutations in SEC23B Gene Causing Congenital Dyserythropoietic Anemia Type II

Congenital dyserythropoietic anemia type II (CDA II) is an inherited autosomal recessive blood disorder which belongs to the wide group of ineffective erythropoiesis conditions. It is characterized by mild to severe normocytic anemia, jaundice, and splenomegaly owing to the hemolytic component. This often leads to liver iron overload and gallstones. CDA II is caused by biallelic mutations in the SEC23B gene. In this study, we report 9 new CDA II cases and identify 16 pathogenic variants, 6 of which are novel. The newly reported variants in SEC23B include three missenses (p.Thr445Arg, p.Tyr579Cys, and p.Arg701His), one frameshift (p.Asp693GlyfsTer2), and two splicing variants (c.1512-2A>G, and the complex intronic variant c.1512-3delinsTT linked to c.1512-16_1512-7delACTCTGGAAT in the same allele). Computational analyses of the missense variants indicated a loss of key residue interactions within the beta sheet and the helical and gelsolin domains, respectively. Analysis of SEC23B protein levels done in patient-derived lymphoblastoid cell lines (LCLs) showed a significant decrease in SEC23B protein expression, in the absence of SEC23A compensation. Reduced SEC23B mRNA expression was only detected in two probands carrying nonsense and frameshift variants; the remaining patients showed either higher gene expression levels or no expression changes at all. The skipping of exons 13 and 14 in the newly reported complex variant c.1512-3delinsTT/c.1512-16_1512-7delACTCTGGAAT results in a shorter protein isoform, as assessed by RT-PCR followed by Sanger sequencing. In this work, we summarize a comprehensive spectrum of SEC23B variants, describe nine new CDA II cases accounting for six previously unreported variants, and discuss innovative therapeutic approaches for CDA II.

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.

[Counting reticulocytes: new importance of an old method]

In clinical practice, the reticulocyte count is the most useful method to estimate red cell life span and red cell production. However, experience of hematologists as well as surveys have shown that counting of reticulocytes is often neglected in the diagnostic work-up of unclassified anemias, and many physicians have difficulties in interpreting the results. Formerly, this was partly due to the low precision of manual counts. Today, this method is largely replaced by flow cytometry, available in almost all larger systems for automated blood count analysis, at low costs and sufficient analytic precision. Interpretation is supported by calculated parameters such as the Reticulocyte Production Index. Here, the authors discuss the limits of the analytic methods and the problems of interpretation in the context of the laboratory profile and the clinical setting.

The congenital dyserythropoietic anemias

The congenital dyserythropoietic anemias (CDAs) are a heterogeneous group of hereditary disorders that seem to be restricted to the erythroid lineage. They are characterized by morphologic abnormalities of erythroid precursors in the bone marrow, resulting in ineffective erythropoiesis and a suboptimal reticulocyte response. As with many rare disorders, cases of CDA are often misdiagnosed, which may lead to inappropriate management. In this review, the authors highlight the relevant clinical data together with recent molecular advances that should aid decision making in diagnosis and patient management.