Aplastic Anemia – Top USMLE Diseases

Aplastic anemia (AA) is a rare, life-threatening condition characterized by pancytopenia and hypocellularity of the bone marrow (in the absence of any abnormal cells) reflecting damage to hematopoietic stem cells. Aplastic anemia can be acquired or inherited, however, most cases of AA are acquired and caused by autoimmune damage to hematopoietic stem cells. Specifically known acquired causes and associations of AAs include medications, chemicals, high doses of whole-body radiation, viral infections, immune diseases, and pregnancy. Inherited or constitutional syndromes associated with AA include Fanconi anemia, dyskeratosis congenita, and Down syndrome. Therapies include transfusion support, immunosuppression, and bone marrow transplantation.

Myelodysplastic syndromes (MDS) are a group of clonal neoplasms with maturation defects characterized by dysplasia, cytopenia, and immature bone marrow precursors. Myelodysplastic syndromes can be idiopathic, or secondary to various injurious exposures such as cytotoxic chemotherapy, ionizing radiation, or environmental toxins. The median patient age is 70 years old. Presentation includes symptoms of anemia (fatigue), neutropenia (infection), or thrombocytopenia (bleeding). The diagnosis is based on bone marrow evaluation, which reveals cytopenia, dysplasia in at least 1 lineage, and blast cells in < 20% of marrow cellularity. Cytogenetic and molecular studies are required for classification, prognosis, and therapy-related decisions. An increased cumulative risk of transformation to AML is present and varies depending on MDS subtype. Management includes supportive care, use of hematopoietic growth factors, immunosuppressive therapy, and allogeneic hematopoietic cell transplantation.

Anemia is a condition in which individuals have low Hb levels, which can arise from  various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia may occur from blood loss, decreased RBC production such as in iron deficiency, or increased RBC destruction such as in hemolysis. Management is aimed at improving Hb levels and treating the underlying conditions.