MDS-516 A Rare Case of X-Linked Recessive Sideroblastic Anemia (XLSA) Masquerading as Myelodysplastic Syndrome-Refractory Anemia With Ringed Sideroblasts (MDS - RARS)

Abstract

XLSA may be confused clinically with MDS-RARS, which can have patient management implications. Sideroblastic anemia is categorized as a rare type of anemia by National Organization for Rare Disorders. Fewer than 200 cases with less than 100 unrelated probands have been described for X-linked recessive sideroblastic anemia (XLSA). XLSA is the most common type of non-syndromic congenital sideroblastic anemias (CSA), with almost 40% of all CSA cases involving mutations in the ALAS2 (δ- aminolaevulinic acid synthase) gene. Male patients (two-thirds of known cases) usually present in childhood or adolescence with symptoms of anemia, while female patients present in middle age. We present a case of XLSA in a male patient with symptom-onset in middle age. He initially presented with symptoms of anemia and received multiple blood transfusions over a period of 10 years. Subsequent bone marrow biopsy showed a hypercellular bone marrow with erythroid hyperplasia, increased iron and ringed sideroblasts consistent with refractory anemia with ringed sideroblasts, no abnormal karyotype in cytogenetics, and normal flow cytometry results. A liver biopsy showed hemosiderotic changes, and he was initially considered to have myelodysplastic syndrome-refractory anemia with ringed sideroblasts (MDS-RARS). Genetic testing, including SF3B1 gene mutation, revealed no findings suggestive of MDS. The patient was then started on iron chelating agents and pyridoxine with improvement in anemia and did not require any further transfusions with significant improvement in his symptoms. A hereditary anemia NGS gene sequencing and deletion/duplication panel was then done which showed pathogenic X-linked recessive hemizygous mutation involving ALAS2 gene-OMIM 301300. Response to the pyridoxine treatment, absence of SF3B1 gene mutation, and presence of ALAS2 gene mutation helped confirm the diagnosis of XLSA in our patient. This case report highlights the necessity for extensive workup in patients with sideroblastic anemia, given the rarity of XLSA and similarity in its clinical symptoms to MDS-RARS, and the need for its early diagnosis. In our patient, iron overload and subsequent liver cirrhosis developed due to multiple transfusions for refractory sideroblastic anemia which was treated as MDS-RARS and could have been avoided if XLSA had been suspected earlier in the course of the disease.