A 31–year–old African American male with no medical history presented to the hospital from prison with worsening fatigue, nausea and abdominal discomfort for several weeks. He also reported lightheadedness and unintentional weight loss of 20 lbs. over the past year. He denied any fevers, syncope, chest pain, emesis or changes in bowel or bladder function. He denied substance abuse while incarcerated, and had negative PPD and HIV test while in prison. Physical exam was unremarkable. Laboratory analysis revealed pancytopenia with white blood cell count (WBC) 3.9, hemoglobin (Hgb) 4.6 (normocytic indices), and platelets 62,000. He was transfused red blood cells with mild response. Peripheral blood smear showed evidence of hemolysis with schistocytes and ovalocytes. Lab studies were also remarkable for LDH 8,600 and haptoglobin <10 supporting hemolysis. Bone marrow biopsy was obtained and showed hypercellularity with trilineage dysplasia. Further work–up including comprehensive metabolic panel, iron studies, DIC labs, direct Coombs test, ceruloplasmin, hepatitis serologies, and HIV test was unremarkable. Significantly, vitamin B12 level was low at 149 pg/ml, and serum methylmalonic acid and homocysteine levels were elevated. The patient was started on IV then oral B12 supplementation and his pancytopenia resolved over days while LDH decreased. He then underwent vitamin B12 deficiency work–up which revealed positive antiparietal cell antibodies, negative intrinsic factor antibodies, elevated gastrin level, and stomach biopsy positive for autoimmune gastritis consistent with a diagnosis of pernicious anemia. His symptoms gradually improved and he was discharged on vitamin B12 supplementation.
Vitamin B12 plays an important role in DNA synthesis and neurologic function. Deficiency can lead to hematologic and neurologic disorders that can often be reversed by early diagnosis and treatment. Although vitamin B12 deficiency is most commonly associated with megaloblastic anemia, it can rarely present as pancytopenia due to ineffective hematopoiesis. This can lead to cell lysis which can be detected on lab evaluation. A sensitive method of detecting vitamin B12 deficiency is measurement of serum methylmalonic acid and homocysteine levels which are increased early in vitamin B12 deficiency. Furthermore, pernicious anemia is a common cause for vitamin B12 deficiency traditionally seen in older Caucasian populations, but now increasingly recognized in younger African American populations. Use of the Schilling test for diagnosis of pernicious anemia has been largely replaced by serologic testing for parietal cell and intrinsic factor antibodies.
This case highlights vitamin B12 deficiency as a rare cause of pancytopenia. In addition, this case is unique in that pernicious anemia is most commonly seen in Caucasians but is increasingly being recognized in younger African American populations.