Pernicious anemia predominates among Mexican adults with vitamin B12 deficiency: clinical and laboratory findings from a tertiary referral center

Background Vitamin B12 deficiency is a reversible cause of hematologic and neurologic morbidity, but its etiologic spectrum in Latin American referral centers remains poorly defined. Methods We retrospectively studied consecutive adults with vitamin B12 deficiency evaluated in hematology and oncology clinics at a Mexican tertiary referral center from January 2013 to July 2023. Etiologies were classified as pernicious anemia, non-surgical malabsorption, post-surgical malabsorption, reduced intake, drug-related causes, or unknown, and pernicious anemia was compared with all other etiologies. Results Among 270 patients (median age 64 years; 52% female), pernicious anemia was the most frequent etiology (52.6%), followed by non-surgical malabsorption (28.1%) and post-surgical states (7.7%). Compared with other causes, pernicious anemia was associated with more comorbidities, lower hemoglobin, lower platelet counts, lower vitamin B12 levels, higher mean corpuscular volume, higher mean corpuscular hemoglobin, and higher indirect bilirubin. Weight loss, gastrointestinal symptoms, and neurologic alterations were common in both groups. Conclusions In this tertiary Mexican cohort, pernicious anemia was the leading identified cause of vitamin B12 deficiency and showed greater hematologic and biochemical severity. Importantly, patients with non-pernicious etiologies had a median MCV within the normocytic range, supporting systematic etiologic evaluation and avoiding overreliance on macrocytosis alone.