Intrinsic factor deficiency in adults with normal hydrochloric acid production

Area of Science:

• Gastroenterology
• Immunology
• Hematology

Background:

• Intrinsic factor is crucial for vitamin B12 absorption.
• Pernicious anemia is an autoimmune condition affecting intrinsic factor production.
• Pernicious anemia typically involves parietal cell antibodies and gastric atrophy.

Observation:

• Two adult cases presented with intrinsic factor deficiency and normal hydrochloric acid production.
• Both patients exhibited significantly reduced intrinsic factor secretion.
• Substantial titers of type I (blocking) intrinsic factor antibodies were detected, but no parietal cell antibodies were found via immunofluorescence.

Findings:

• The absence of parietal cell antibodies differentiates these cases from typical pernicious anemia.
• The presence of blocking intrinsic factor antibodies suggests an autoimmune mechanism targeting intrinsic factor directly.
• These findings challenge conventional understanding of pernicious anemia pathogenesis.

Implications:

• These cases may represent congenital intrinsic factor deficiency presenting in adulthood.
• They could be early-stage pernicious anemia before gastric mucosal changes occur.
• A novel syndrome of isolated intrinsic factor deficiency is a possibility requiring further investigation.