Schilling test:

• oral radiolabeled vit B12 + intramuscular injection of unlabeled vit B12 an hour later
• urine collection for 24 hours

Normal test: >10% of radiolabeled B12 in the urine

Impaired absorption: <10%

This patient has impaired absorption and it is corrected by oral intrinsic factor

Atrophic gastritis chronic inflammation causing pernicious anemia --> auto Ab against parietal cells or intrinsic factor

• Middle-aged woman with history of autoimmune disease who presents with megaloblastic anemia + neurologic symptoms with an abnormal Schilling test corrected by administration of intrinsic factor, most consistent with Autoimmune gastritis (antibodies against parietal cells in the stomach lead to (1) impaired intrinsic factor production –> B12 deficiency (2) chronic inflammation –> chronic/atrophic gastritis
• Key idea: B12 deficiency leads to subacute combined degeneration, which often leads to problems with strength, fine touch, vibration and balance/cerebellar functions

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