A Rare Case of Down Syndrome with Severe Pancytopenia: Clinical Analysis and Literature Review

Objective To investigate the etiology and diagnostic approach of pancytopenia in children, with emphasis on uncommon nutritional causes, particularly in individuals with intellectual disability, whose dietary behaviors may predispose them to deficiency. The goal is to reduce misdiagnosis and therapeutic delays in clinical practice. Methods We retrospectively analyzed the clinical features, laboratory results, bone marrow findings, treatment, and outcomes of a child with trisomy 21 presenting with profound pancytopenia at Zaozhuang Municipal Hospital in November 2023, supplemented by a review of the literature. Results The patient exhibited severe pancytopenia at admission with WBC = 1.77×10⁹/L, RBC = 0.47×10¹²/L, hemoglobin = 21 g/L, and platelets = 5×10⁹/L. Bone marrow morphology, immunophenotyping, and serum folate/vitamin B12 assays confirmed megaloblastic anemia. Following folate and vitamin B12 replacement therapy, hematologic parameters progressively normalized. Conclusion The child was diagnosed with severe megaloblastic anemia (MA). MA typically causes macrocytic anemia and may lead to pancytopenia, although the case of profound pancytopenia with such severity is rare in the pediatric population in China. In cases with extremely low blood counts, differentiation from leukemia, myelodysplastic syndromes, and aplastic anemia is critical. Bone marrow aspiration and biopsy remain essential. Vitamin B12 deficiency in this case resulted in neuropsychiatric symptoms, including seizures, which improved substantially after vitamin replacement. This case underscores the importance of evaluating nutritional status in children with developmental delay and restricted dietary patterns.