Post-COVID-19 vitamin B12 deficiency presenting as pseudo-thrombotic microangiopathy: a case report and review of diagnostic pitfalls

Abstract Introduction Vitamin B12 deficiency can rarely manifest as pseudo-thrombotic microangiopathy (PTMA), a hematologic syndrome that mimics thrombotic thrombocytopenic purpura (TTP). This case emphasizes the diagnostic challenge of PTMA in elderly, post-COVID-19 patients, and highlights the importance of distinguishing it from true TMA to avoid unnecessary treatment. Case presentation A 77-year-old woman with a recent history of COVID-19 infection presented with fatigue, delirium, severe anemia (hemoglobin 3.3 g/dL), acute kidney injury, elevated LDH, schistocytosis, and glossitis. Her clinical picture initially raised suspicion for thrombotic microangiopathy (TMA). However, further evaluation revealed macrocytic anemia and intramedullary hemolysis. The absence of severe thrombocytopenia and the presence of macrocytosis and highly elevated LDH suggested PTMA due to vitamin B12 deficiency. She was treated with high-dose intramuscular vitamin B12 (2,000 µg/day), resulting in rapid clinical and hematologic improvement. The patient was discharged after 16 days with full recovery of renal function and stable hemoglobin. Conclusion This case illustrates the importance of considering vitamin B12 deficiency in patients with TMA-like features, particularly when macrocytosis is present. Early recognition of PTMA can prevent unnecessary invasive therapies and promote rapid recovery through appropriate supplementation.