Program: Oral and Poster Abstracts
Session: 101. Red Cells and Erythropoiesis, Structure and Function, Metabolism, and Survival, Excluding Iron: Poster I
The now 4-years old Turkish boy was born after 32 weeks of gestation and presented with a severe hemolytic anemia (Hb 40 g/L) that required exchange transfusions and a complete dRTA that was treated with oral bicarbonate. He also suffered from delayed psychomotoric developmental with failure to thrive, trigonocephalus and strabismus convergens. Bone marrow smears showed marked dyserythropoiesis but normal myeloid and megakaryocytic lineages. Although necessary monthly transfusions impeded the patient's direct diagnostic work-up, a flow cytometric eosin-5-maleimide assay eventually revealed a reduced staining of his consanguine parents' and his two siblings' erythrocytes, who all had subclinical signs of spherocytosis despite normal RBC counts.
Based on these findings, we analyzed the SLC4A1gene and found two homozygous sequence variants in the patient, namely a novel disease-relevant exon 12 nonsense mutation c.1430C>A (p.Ser477X) and a disease-unrelated c.2312-48T>G (rs13306780). The ensuing stop codon of the former truncates the protein, prevents band 3 formation and reduces glycophorin A expression. Bright field imaging uncovered few phenotypic spherocytic band 3 null RBCs even in the peripheral blood.
In accordance with the autosomal recessive inheritance pattern, both healthy parents as well as his healthy siblings were found to be heterozygous carriers. The band 3 protein was reduced to 50-60% in the parents’ erythrocytes. An increased approximately 22 kDa-sized band was evident in Coomassie stained gels of the heterozygous mutation carriers' membrane preparations and classified by immunoblotting as peroxiredoxin 2 (PRDX2), which plays a major role in protecting RBCs from oxidative stress.
Taken together, the provided data clearly confirm the relevance of this particular c.1430C>A (p.Ser477X) SLC4A1 mutation in the disease process. Of note, such a severe dyserythropoietic anemia and complete dRTA was also recently reported in a patient with Southeast Asian ovalocytosis and another form of homozygous SLC4A1 mutation (Picard et al, Blood 123:1963;2014).
Disclosures: No relevant conflicts of interest to declare.
See more of: Red Cells and Erythropoiesis, Structure and Function, Metabolism, and Survival, Excluding Iron
See more of: Oral and Poster Abstracts
*signifies non-member of ASH