Multifaceted Clinical Spectrum of Vitamin B12 Deficiency - a Case Report and Literature Review

Vitamin B12 (cobalamin) deficiency is a well-known cause of hematologic and neurological disorders; however, its presentation can be highly variable, leading to diagnostic challenges. The etiology is diverse: while the most common cause is dietary insufficiency, other potential causes include malabsorption syndromes, autoimmune gastritis, gastrointestinal disorders, chronic infections, and genetic defects. Clinical presentation varies significantly, ranging from clinically silent macrocytosis to life-threatening anemia or pancytopenia. Neurological and psychiatric manifestations may include vision and gait impairment, depression, and cognitive dysfunction. Given this complexity, vitamin B12 deficiency can mimic other conditions, often leading to a delay in diagnosis. A 15-year-old male was admitted in critical condition with severe anemia, thrombocytopenia, jaundice, progressive weight loss, fatigue, gait disturbances, and vision impairment. Initially, Evan's syndrome was suspected, but further laboratory investigations, including a peripheral blood smear and elevated mean corpuscular volume (MCV), led to the diagnosis of profound vitamin B12 deficiency. Additional workup revealed chronic atrophic gastritis as the underlying cause. The patient was treated with vitamin B12 injections, leading to significant hematologic and neurological improvement, weight gain, and resolution of psychiatric symptoms. However, optic nerve atrophy was detected as a late complication. This case emphasizes the need to consider vitamin B12 deficiency in pediatric patients with unexplained hematologic, neurological, and psychiatric symptoms, particularly when associated with chronic atrophic gastritis. Early recognition and intervention are crucial to preventing irreversible complications, such as optic neuropathy. Given the multidisciplinary nature of its presentation, this case serves as an important reminder for pediatricians, hematologists, gastroenterologists, and neurologists to maintain a high index of suspicion for vitamin B12 deficiency in complex clinical scenarios.