Megaloblastic Anemia with Ring Sideroblasts is not Always Myelodysplastic Syndrome

Vitamin B12 deficiency in an infant with neurological and hematological findings: A case report

Key Clinical Message

It is important for pregnant and breastfeeding women who adhere to a strict vegetarian diet to take appropriate steps to avoid vitamin B12 deficiency in their infants.

Abstract

Vitamin B12 deficiency is rare during infancy. The initial symptoms of this deficiency are subtle and may include irritability, failure to thrive with a decline in growth rate, apathy, anorexia, refusal of solid foods, megaloblastic anemia, and developmental regression. The case presented here involves an 8-month-old male infant who showed neurological symptoms such as decreased activity, increased drowsiness, and reduced interaction with parents, which were ultimately linked to a deficiency of cobalamin (vitamin B12). Early recognition of this condition is critical because it is reversible. Therefore, pregnant and lactating women who follow a strict vegetarian diet should take necessary measures to prevent vitamin B12 deficiency in infants.

Causes and Pathophysiology of Acquired Sideroblastic Anemia

The sideroblastic anemias are a heterogeneous group of inherited and acquired disorders characterized by anemia and the presence of ring sideroblasts in the bone marrow. Ring sideroblasts are abnormal erythroblasts with iron-loaded mitochondria that are visualized by Prussian blue staining as a perinuclear ring of green-blue granules. The mechanisms that lead to the ring sideroblast formation are heterogeneous, but in all of them, there is an abnormal deposition of iron in the mitochondria of erythroblasts. Congenital sideroblastic anemias include nonsyndromic and syndromic disorders. Acquired sideroblastic anemias include conditions that range from clonal disorders (myeloid neoplasms as myelodysplastic syndromes and myelodysplastic/myeloproliferative neoplasms with ring sideroblasts) to toxic or metabolic reversible sideroblastic anemia. In the last 30 years, due to the advances in genomic techniques, a deep knowledge of the pathophysiological mechanisms has been accomplished and the bases for possible targeted treatments have been established. The distinction between the different forms of sideroblastic anemia is based on the study of the characteristics of the anemia, age of diagnosis, clinical manifestations, and the performance of laboratory analysis involving genetic testing in many cases. This review focuses on the differential diagnosis of acquired disorders associated with ring sideroblasts.

Sideroblastic anaemia in a patient with sickle cell disease

Sideroblastic anaemia is a rare condition. We report a unique case of concomitant sideroblastic anaemia in a patient with sickle cell disease with long-standing blood transfusion history. Due to a low prevalence of sideroblastic anaemia, the diagnosis of sideroblastic anaemia is often difficult, especially when coexisting with common types of anaemia, including sickle cell disease. This case highlights the detrimental effects of anchoring bias. Rare causes of refractory anaemia should be considered in patients with haemoglobin disorders as the therapeutic approaches for these conditions are different. High suspicion on the part of the clinician and low threshold for workup of anaemia often aids in the diagnosis of coexisting conditions such as sideroblastic anaemia. Early diagnosis and treatment of sideroblastic anaemia improves patient outcomes and prevents long-term complications.

Peripheral Blood and Bone Marrow Findings in Chronic Alcoholics with Special Reference to Acquired Sideroblastic Anemia

Anemia associated with alcoholism has numerous causes, most common being megaloblastic anemia and acquired sideroblastic anemia (SA). The bone marrow aspirate (BMA) and bone marrow iron (BMIr) findings and their correlation with peripheral blood smear (PBS) have not been extensively described in literature. We aim to study the spectrum of hematological abnormalities in chronic alcoholics. Complete blood count (CBC), PBS, BMA and BMIr of 71 chronic alcoholics were studied retrospectively over a period of 3 years. The slides were reviewed by 2 pathologists. The clinical history, CBC, PBS, BMA and BMIr findings were recorded. Out of 71 patients, 68 (95.77%) had anaemia. Red cell morphology varied from normocytic-normochromic, microcytic-hypochromic, macrocytic, to dimorphic anaemia. Principal findings seen on BMA were erythroid hyperplasia and megaloblastic maturation. BMIr was available in 41 patients; iron stores were decreased in 2 (4.88%), normal in 14 (34.15%), increased in 25 (60.97%). Seven (17.07%) cases showed presence of ring sideroblasts. Chronic alcoholics show a variety of abnormalities in BMA, which closely mimic many haematological disorders. A history of alcoholism should always be taken in these circumstances. SA should be ruled out in all chronic alcoholics with anaemia not responding to vitamin B₁₂/folic acid, even with macrocytic picture on PBS.

Molecular pathophysiology and genetic mutations in congenital sideroblastic anemia

Sideroblastic anemia is a heterogeneous congenital and acquired disorder characterized by anemia and the presence of ring sideroblasts in the bone marrow. Congenital sideroblastic anemia (CSA) is a rare disease caused by mutations in genes involved in the heme biosynthesis, iron-sulfur [Fe-S] cluster biosynthesis, and mitochondrial protein synthesis. The most prevalent form of CSA is X-linked sideroblastic anemia, caused by mutations in the erythroid-specific δ-aminolevulinate synthase (ALAS2), which is the first enzyme of the heme biosynthesis pathway in erythroid cells. To date, a remarkable number of genetically undefined CSA cases remain, but a recent application of the next-generation sequencing technology has recognized novel causative genes for CSA. However, in most instances, the detailed molecular mechanisms of how defects of each gene result in the abnormal mitochondrial iron accumulation remain unclear. This review aims to cover the current understanding of the molecular pathophysiology of CSA.