Pseudothrombotic microangiopathy resulting from severe vitamin B12 deficiency in a pediatric patient with autism: A case report

Vitamin B12 deficiency is typically characterized by megaloblastic anemia, but can also rarely present with pseudomicroangiopathic hemolytic anemia or multilineage cytopenias secondary to dyserythropoiesis and apoptotic cell death. We describe a 12-year-old male with autism spectrum disorder who presented with fever, night sweats, and weight loss. Laboratory testing identified severe neutropenia and hemolytic anemia, and an undetectably low vitamin B12 level. Dietary history confirmed significant food restriction over the preceding 6 months. He received 1000 µg of intramuscular vitamin B12 daily for 7 days and subsequently transitioned to oral therapy. His hemoglobin, hemolytic markers, and neutrophil count normalized within 13 days of vitamin B12 initiation. Our report describes a rare and severe manifestation of vitamin B12 deficiency in a patient with autism spectrum disorder and emphasizes the importance of screening for micronutrient deficiencies among vulnerable pediatric populations to avoid unnecessary and invasive testing.