Differential Diagnosis for Mean Cell Volume (MCV) of 108 in a 75-year-old

Single Most Likely Diagnosis

• Vitamin B12 Deficiency: This is a common cause of macrocytic anemia, especially in the elderly. Vitamin B12 deficiency can lead to elevated MCV due to impaired DNA synthesis, affecting red blood cell production. The elderly are at higher risk due to decreased absorption, dietary deficiencies, or use of medications that interfere with B12 absorption.

Other Likely Diagnoses

• Folate Deficiency: Similar to vitamin B12, folate deficiency can cause macrocytic anemia. It's less common than B12 deficiency but still a consideration, especially in alcoholics, those with poor diets, or individuals with conditions affecting the small intestine.
• Alcohol Abuse: Chronic alcohol consumption can lead to macrocytosis due to its direct toxic effect on bone marrow, leading to impaired red blood cell production. Alcohol also interferes with folate metabolism, further contributing to elevated MCV.
• Hypothyroidism: Although less common, hypothyroidism can cause macrocytic anemia. The mechanism is not fully understood but may involve decreased production of erythropoietin or a direct effect on bone marrow.

Do Not Miss Diagnoses

• Myelodysplastic Syndrome (MDS): This group of disorders is characterized by ineffective blood cell production. MDS can present with macrocytic anemia and is more common in the elderly. It's crucial to diagnose MDS due to its potential progression to acute myeloid leukemia and the availability of specific treatments.
• Chronic Liver Disease: Liver disease can lead to macrocytosis due to impaired liver function affecting vitamin B12 and folate metabolism, as well as the production of lipoproteins that are essential for red blood cell membrane synthesis.

Rare Diagnoses

• Aplastic Anemia: Although typically presenting with pancytopenia, some cases of aplastic anemia can have a macrocytic component due to the bone marrow's attempt to compensate for the lack of red blood cell production.
• Pernicious Anemia: An autoimmune condition leading to vitamin B12 deficiency due to the lack of intrinsic factor necessary for B12 absorption. It's less common than other causes of B12 deficiency but should be considered, especially in patients with other autoimmune diseases.
• Medication-induced Macrocytosis: Certain medications, such as methotrexate, hydroxyurea, and some anticonvulsants, can cause macrocytosis. The elderly are often on multiple medications, making this a consideration, especially if the onset of macrocytosis correlates with the initiation of a new drug.