Does HLA-DQ8–associated celiac disease cause malabsorption of folate and vitamin B12 and lead to anemia?

Active celiac disease is an immune-mediated enteropathy triggered by gluten ingestion in genetically susceptible individuals, resulting in profound systemic and hematologic consequences.

Genetic susceptibility and molecular mechanisms

• HLA-DQ8 Antigen Presentation: The HLA-DQ8 heterodimer (encoded by DQA1*03 and DQB1*03:02) serves as a primary genetic driver. In the lamina propria, tissue transglutaminase 2 (TG2) deamidates gluten peptides, introducing negative charges that dramatically increase their binding affinity to HLA-DQ8.
• T-Cell Activation: Antigen-presenting cells present these stable HLA-DQ8-gluten complexes to CD4+ T cells. This triggers a Th1-mediated inflammatory cascade, leading to the mucosal damage characteristic of celiac disease. HLA typing (DQ2/DQ8) holds a 98% to 100% negative predictive value, making it highly effective for ruling out the condition.

Mucosal damage and anemia pathways

• Proximal Malabsorption: Immune-mediated villous atrophy is classically most severe in the duodenum and proximal jejunum. Because these areas are the primary sites for folate and iron uptake, mucosal degradation directly impairs absorption, causing folate deficiency in 20% to 40% of newly diagnosed patients.
• Distal Extension and Secondary Factors: Vitamin B12 is absorbed in the terminal ileum. Cobalamin deficiency occurs in 5% to 20% of untreated patients, driven by the distal extension of severe mucosal lesions into the ileum or secondary complications like small intestinal bacterial overgrowth.
• Hematologic Impact: The combined malabsorption of iron, folate, and vitamin B12 directly drives the development of anemia, which is present in 25% to 55% of patients at celiac diagnosis.

Bottom line

• HLA-DQ8 is a validated genetic risk factor that presents deamidated gluten to drive proximal small-bowel enteropathy, resulting in the malabsorption of iron, folate, and vitamin B12, and presenting clinically as multifactorial anemia.