Differential Diagnosis for Low Hb and High MCV
Single Most Likely Diagnosis
- Vitamin B12 or Folate Deficiency: This is the most common cause of macrocytic anemia (high MCV), leading to low hemoglobin (Hb) levels. The deficiency impairs DNA synthesis, resulting in the production of larger than normal red blood cells.
Other Likely Diagnoses
- Alcohol Abuse: Chronic alcohol consumption can lead to macrocytic anemia due to its toxic effects on the bone marrow and the potential for associated nutritional deficiencies.
- Hypothyroidism: Although less common, hypothyroidism can cause macrocytic anemia, possibly due to decreased production of erythropoietin or other metabolic effects.
- Liver Disease: Certain liver conditions can lead to macrocytic anemia, possibly due to impaired liver function affecting vitamin B12 and folate metabolism or storage.
Do Not Miss Diagnoses
- Myeloproliferative Neoplasms (e.g., Polycythemia Vera, Primary Myelofibrosis): While these conditions more commonly present with elevated blood cell counts, in some cases, they can lead to macrocytic anemia, especially if there is significant bone marrow fibrosis or if the disease is in a spent phase.
- Paroxysmal Nocturnal Hemoglobinuria (PNH): A rare, acquired, life-threatening disease of the blood characterized by the destruction of red blood cells, activation of the coagulation system, and impaired bone marrow function, which can sometimes present with macrocytic anemia.
- Bone Marrow Failure Syndromes (e.g., Aplastic Anemia, Myelodysplastic Syndromes): These conditions can present with macrocytic anemia among other cytopenias, and are critical to diagnose due to their potential for severe complications and the need for specific management strategies.
Rare Diagnoses
- Orotic Aciduria: A rare genetic disorder affecting pyrimidine synthesis, leading to macrocytic anemia.
- Congenital Dyserythropoietic Anemias: A group of rare genetic disorders characterized by ineffective erythropoiesis and often macrocytic anemia.
- Pernicious Anemia due to Intrinsic Factor Deficiency or Gastric Resection: While not as common as other causes of vitamin B12 deficiency, these conditions can lead to macrocytic anemia and are important to consider, especially in patients with a history of gastric surgery or autoimmune disorders.