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

EGLN1 mutations in Cis can induce congenital erythrocytosis with thromboses by increasing protein instability

Hereditary congenital erythrocytosis results from constitutive activation of the hypoxia pathway. This pathway is controlled by regulation of the α isoforms of the hypoxia-inducible factor α/β heterodimer, notably via hydroxylation by prolyl hydroxylase domain 2 (PHD2). Mutations affecting PHD2 are involved in Type 3 erythrocytosis. We report an atypical family bearing two PHD2 mutations located in Cis (L195H and E225D) transmitted in a dominant feature, together with a phenotypic analysis, structural modelling and functional study. Mutations have a cumulative effect, with E255D playing the major role, and severely compromised PHD2 stability, probably explaining why the hypoxia pathway at the origin of the disease is activated.

Identification of a novel splice variant in SEC23B gene in a patient with concomitant presence of congenital dyserythropoietic anemia II and Gilbert's syndrome

BACKGROUND

Congenital dyserythropoietic anemia Ⅱ (CDA Ⅱ) is a rare inherited disorder of defective erythropoiesis caused by SEC23B gene mutation. CDA Ⅱ is often misdiagnosed as a more common type of clinically related anemia, or it remains undiagnosed due to phenotypic variability caused by the coexistence of inherited liver diseases, including Gilbert's syndrome (GS) and hereditary hemochromatosis.

METHODS

We describe the case of a boy with genetically undetermined severe hemolytic anemia, hepatosplenomegaly, and gallstones whose diagnosis was achieved by targeted next generation sequencing.

RESULTS

Molecular analysis revealed a maternally inherited novel intronic variant and a paternally inherited missense variant, c.[994-3C > T];[1831C > T] in the SEC23B gene, confirming diagnosis of CDA Ⅱ. cDNA analysis verified that the splice acceptor site variant results in two mutant transcripts, one with an exon 9 skip and one in which exons 9 and 10 are deleted. SEC23B mRNA levels in the patient were lower than those in healthy controls. The patient was also homozygous for the UGT1A1*6 allele, consistent with GS.

CONCLUSION

Identification of the novel splice variant in this study further expands the spectrum of known SEC23B gene mutations. Molecular genetic approaches can lead to accurate diagnosis and management of CDA Ⅱ patients, particularly for those with GS coexisting.

Congenital Dyserythropoietic Anemia Type II With Myelofibrosis in an Adult Patient: A Report of a Rare Case With a Brief Review

Congenital dyserythropoietic anemias (CDAs) are rare hereditary disorders, of which type II CDA is the most common. Mutations in the SEC23B gene located on chromosome 20 result in this autosomal recessive disorder. In this case report, we present a case of CDA II with unique biopsy findings being detected via genetic testing. A female aged 30 years presented with major complaints of pallor weakness and easy fatiguability since childhood. The patient gave a history of 25 units of blood transfusion, the majority of which were transfused during pregnancy, followed by regular transfusions thereafter. On examination, all her vitals were in the normal range. Pallor, frontal bossing, and malocclusion of teeth were noted. Her laboratory workup showed the following: hemoglobin (Hb): 3.7 g/dl; mean corpuscular volume: 83 fl; mean corpuscular Hb: 29 g/dl; mean corpuscular Hb concentration: 34.9 g/dl; red cell distribution width: 30.4%; reticulocyte count (RC): 6.2%; corrected RC: 1.3%; lactate dehydrogenase: 441 IU/L; direct Coombs test/indirect Coombs test: negative; serum iron: 242 microgram/dl; transferrin saturation: 96.08%; ferritin: 1,880 ng/ml; and normal high-performance liquid chromatography and eosin-5'-maleimide binding test. The peripheral blood film showed normocytic normochromic anemia with anisopoikilocytosis in the form of a few spherocytes. No immature cells were seen. After obtaining the patient's consent, we performed a hereditary hemolytic anemia gene analysis test, which showed homozygous missense variation in exon 12 of the SEC23B gene. The bone marrow examination showed hyperplasia in the erythroid series with dyserythropoiesis, and surprisingly, myelofibrosis grade I-II (WHO 2017) was also observed on biopsy. Patients with CDA type II generally present with variable degrees of anemia along with pallor, icterus, splenomegaly, gallstones, and iron overload. In our case, the diagnosis of CDA type II was made at an adult age. Also, evidence of myelofibrosis was noted in our case, making it worth reporting. The use of a hereditary hemolytic anemia gene analysis panel test came as a rescue for its exact diagnosis. This case report emphasizes the role of molecular genetic testing for early and accurate diagnosis, which, in turn, could help in appropriate treatment planning and proper genetic counseling. The prevalence of CDA type II is still vaguely known; hence, extensive workup of persistent anemias and proper follow-up would be beneficial.

Congenital dyserythropoietic anemia type II in a newborn with a novel compound heterozygous mutation in the SEC23B: a case report and review of the literature

Congenital dyserythropoietic anemia type II (CDA II) refers to a group of extremely rare heterozygous disorders characterized by ineffective erythropoiesis and morphological abnormalities of erythrocytes and bone marrow erythroblasts. Six types of CDA with differing heterogenous genetic mutations have been identified to date. Due to the genetic and clinical heterogeneity of CDA, accurate diagnosis can be very challenging, especially with the clinical overlap observed between CDA and other dyserythropoietic diseases. A 1-month-old infant girl, born to a non-consanguineous family, presented with severe normocytic anemia that required transfusions every 2 to 3 weeks since birth, as well as jaundice. Whole exome sequencing revealed a novel compound heterozygosity in the SEC23B gene, thus establishing the diagnosis of CDA II. Analysis by multiple bioinformatics tools predicted that the mutant proteins were deleterious. Here, we report a novel variation in SEC23B that extends the mutation spectrum of SEC23B in the diagnosis of CDA II.