Congenital Dyserythropoietic Anemia Type II Caused by a New SEC23B Sequence Variant

Congenital dyserythropoietic anemias (CDAs) include a heterogeneous group of conditions characterized by insufficient erythropoiesis giving rise to monolinear cytopenia. Based on the morphological features of erythroblasts, three major subtypes have been established: CDA Type I, CDA Type II, and CDA Type III. CDA Type II is the most common type of CDAs, and this disease is characterized by a normocytic anemia with a normal or slightly increased reticulocyte count. The bone marrow is hypercellular with erythroid hyperplasia and binucleated erythroblasts with two nuclei at the same maturation stage. The inheritance is autosomal recessive, and the disease is caused by biallelic mutations in the SEC28B gene. More than 100 pathogenetic variants have been identified. Here, we report on three patients from Somalia with CDA Type II caused by a new SEC23B sequence variant. They came to attention and were diagnosed in early adulthood. Cases 1 and 2 had mild anemia with signs of hemolysis, and Case 3 had mild anemia with reticulocytosis. The eosin-5-maleimide binding test showed reduced binding in all three patients. Molecular genetics disclosed homozygosity for the sequence variant NM_006363.6:c.1580T > C p.(Leu527Ser) in the SEC23B gene. A bone marrow aspirate was performed from Case 2, and the smear disclosed morphological abnormalities typical for CDA Type II.