From the Guidelines
The differential diagnosis for a 61-year-old male with gout on allopurinol, tadalafil (Cialis), and tamsulosin, with a normal Comprehensive Metabolic Panel (CMP) and normal Complete Blood Count (CBC) aside from macrocytosis (elevated Mean Corpuscular Volume (MCV) of 104) includes vitamin B12 or folate deficiency, as macrocytosis is most commonly associated with megaloblastic anemia caused by insufficient uptake or inadequate absorption of these vitamins 1.
Possible Causes of Macrocytosis
- Vitamin B12 or folate deficiency: most common cause of macrocytosis, which can be due to insufficient dietary intake, malabsorption, or increased demand 1
- Medications: certain medications such as allopurinol, hydroxyurea, or diphenytoin can cause macrocytosis 1
- Alcoholism: chronic alcohol abuse can lead to macrocytosis due to nutritional deficiencies and direct toxic effects on the bone marrow 1
- Hypothyroidism: untreated hypothyroidism can cause macrocytosis due to decreased metabolism and nutritional deficiencies 1
- Reticulocytosis: increased production of reticulocytes (immature red blood cells) can cause macrocytosis 1
Diagnostic Approach
To further evaluate the cause of macrocytosis, the following tests should be considered:
- Reticulocyte count: to assess bone marrow production and rule out hemolysis or blood loss 1
- Serum vitamin B12 and folate levels: to diagnose deficiencies and guide supplementation 1
- Iron studies: to rule out iron deficiency or overload, which can also cause anemia 1
- Liver function tests: to assess for liver disease, which can cause macrocytosis due to impaired vitamin B12 and folate metabolism 1
- Thyroid function tests: to rule out hypothyroidism, which can cause macrocytosis 1
From the Research
Differential Diagnosis
The differential diagnosis for a 61-year-old male with gout on allopurinol, tadalafil (Cialis), and tamsulosin, with a normal Comprehensive Metabolic Panel (CMP) and normal Complete Blood Count (CBC) aside from macrocytosis (elevated Mean Corpuscular Volume (MCV) of 104) includes:
- Chronic lymphocytic leukemia (CLL) 2
- Other causes of macrocytosis, such as vitamin B12 or folate deficiency
- Side effects of medications, such as allopurinol or tadalafil
Potential Causes of Macrocytosis
Macrocytosis can be caused by various factors, including:
- Vitamin B12 or folate deficiency
- Alcohol abuse
- Liver disease
- Hypothyroidism
- Certain medications, such as allopurinol or tadalafil
- CLL or other hematologic disorders 2
Relevance of Gout and Urate-Lowering Therapy
The patient's gout and urate-lowering therapy with allopurinol may be relevant to the differential diagnosis, as allopurinol can cause macrocytosis as a side effect 3, 4. However, the patient's normal CMP and CBC aside from macrocytosis suggest that the gout and urate-lowering therapy may not be the primary cause of the macrocytosis.
Need for Further Evaluation
Further evaluation is needed to determine the cause of the macrocytosis and to rule out other potential causes, such as CLL or other hematologic disorders 2. This may include additional laboratory tests, such as vitamin B12 and folate levels, liver function tests, and thyroid function tests, as well as a bone marrow biopsy if CLL is suspected.