The array of diagnostic workup for pyrexia of unknown origin (PUO) generally revolves in searching for infections, inflammatory/autoimmune, and endocrine etiologies. A differential diagnosis of fever, hemolytic anemia, and thrombocytopenia can have etiologies varying from infections like malaria, dengue, cytomegalovirus, Ebstein barr virus, Parvovirus, infective endocarditis, to autoimmune disorder (systemic lupus erythromatosis), vasculitis, hemolytic uremic syndrome, thrombotic thrombocytopenic purpura (TTP), autoimmune hemolytic anemia/Evan's syndrome, paroxysmal nocturnal hemoglobinuri (PNH), or drugs. Nutritional deficiencies (especially vitamin B12 deficiency) as a cause of fever, hemolytic anemia, and thrombocytopenia are very rare and therefore rarely thought of. Severe vitamin B12 deficiency may cause fever and if accompanied by concurrent hyper-homocysteinemia and hypophosphatemia can sometimes lead to severe hemolysis mimicking the above-mentioned conditions. We present a case that highlights vitamin B12 and vitamin D deficiency as an easily treatable cause of PUO, hemolytic anemia, and thrombocytopenia, which should be actively looked for and treated before proceeding with more complicated and expensive investigation or starting empiric treatments.
Keywords: Fever; hemolytic anemia; homocysteine; hypophosphatemia; vitamin B12; vitamin D.