A Simple Vitamin Deficiency With Life-Threatening Complications: A Case of B12 Deficiency and Hyperhomocysteinemia-Induced Thrombosis.

While macrocytic anemia is common in vitamin B12 deficiency, rarely, pancytopenia and hemolytic anemia can occur. Homocysteine levels are elevated in severe B12 deficiency, and this is linked to thrombus formation with potentially life-threatening complications. We present a patient with severe vitamin B12 deficiency complicated by hyperhomocysteinemia and obstructive shock from pulmonary embolism.