Vitamin B12 is essential for neurological function and its deficiency is associated with many neuropsychiatric disorders. We report the case of a previously healthy 53-year-old male patient presenting with delirium and multiple neurological findings. Complete blood analysis indicated megaloblastic anemia. All infectious causes were excluded owing to negative cultures (blood and urine). Tests for human immunodeficiency virus, syphilis, and toxoplasma were also negative. Metabolic workup showed severe vitamin B12 deficiency, decreased reticulocyte count, and increased direct bilirubin and lactate dehydrogenase. Intramuscular injection of cobalamin was started, and the patient showed significant improvement.

One of the most prevalent causes of vasculitis is bacterial infection. An infection that causes anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is uncommon and not reported frequently. We report a case of a 74-year-old male who presented with fever for ten days and was found to have brucellosis. Then, he was diagnosed with Guillain-Barré syndrome (GBS) and started on immunoglobulin (IVIG) for one week without a response. His fever was still persistent despite appropriate antibiotic therapy. Rheumatology evaluation revealed a history of multiple joint pain and swelling, elevated inflammatory marker, and a high titer of P-ANCA. Steroid therapy was started initially on the background of antibiotics therapy. His fever and other symptoms showed marked improvement after one week. However, P-ANCA titer was still elevated. The decision was made to treat the patient as a case of brucellosis-induced P-ANCA vasculitis. Azathioprine was added, and steroid was maintained for one month and then it was tapered gradually. All symptoms improved from the third month of follow-up except weakness from peripheral neuropathy with normalization of P-ANCA titer. His condition remained stable after six months of follow-up. Clinicians should be aware of the possibility of infection-induced vasculitis, particularly when patients’ symptoms persist despite the appropriate use of antibiotics.