Hypothyroidism causing macrocytic anemia unresponsive to B12 and folate

Area of Science:

• Hematology
• Endocrinology
• Autoimmune Disorders

Background:

• Pernicious anemia is an autoimmune condition causing vitamin B12 deficiency.
• Vitamin B12 therapy is standard treatment for pernicious anemia.
• Macrocytic anemia is characterized by elevated mean corpuscular volume (MCV).

Observation:

• A patient with pernicious anemia on long-term vitamin B12 therapy developed a mild macrocytic anemia.
• The anemia did not respond to folic acid or multivitamin supplementation.
• Further investigation was prompted by unexplained elevated MCV and potential associated autoimmune conditions.

Findings:

• Primary hypothyroidism was diagnosed as the cause of the persistent macrocytic anemia.
• Treatment with levothyroxine effectively corrected the hematologic abnormalities within four months.
• This case demonstrates that hypothyroidism can manifest with macrocytic anemia.

Implications:

• Hypothyroidism should be considered in the differential diagnosis of unexplained macrocytic anemia, even in patients with known pernicious anemia.
• Endocrine evaluation may be necessary for patients with persistent macrocytic anemia unresponsive to standard B12 therapy.
• Recognizing the hematologic manifestations of hypothyroidism is crucial for timely diagnosis and effective management.