A 50-year-old woman presented with manifestations of anemia, glossitis, recurrent diarrhea, anorexia, and weight loss. Blood picture showed macrophages, anisocytosis, and poikilocytosis. Serum vitamin B12 levels were low and serum gastrin levels were elevated. What is the diagnosis?
Reading File
Finding Sources
Finding Sources
Reading File
Reading File
Finding Sources
Finding Sources
Reading File
I now have all the information needed for a complete, authoritative answer.
Diagnosis: Pernicious Anemia (Autoimmune Atrophic Gastritis with Vitamin B12 Deficiency)
How Each Clue Fits
| Finding | Explanation |
|---|---|
| 50-year-old woman | Typical patient - median age at diagnosis ~60; females slightly more affected than males |
| Anemia + macrophages, anisocytosis, poikilocytosis | Megaloblastic anemia from B12 deficiency - macrocytes (large RBCs) with shape variation |
| Glossitis | Atrophic glossitis - tongue becomes smooth and "beefy red" due to epithelial megaloblastosis |
| Recurrent diarrhea | Malabsorptive diarrhea from B12 deficiency and gut mucosal megaloblastosis |
| Anorexia and weight loss | Systemic effects of chronic deficiency and gastric mucosal atrophy |
| Low serum B12 | Hallmark finding - loss of intrinsic factor prevents B12 absorption in the terminal ileum |
| Elevated serum gastrin (hypergastrinemia) | Key diagnostic clue - loss of parietal cells causes achlorhydria; lack of acid feedback stimulates antral G cells to overproduce gastrin as compensation |
Pathogenesis (Step-by-Step)
- Autoimmune trigger: CD4+ T cells and antibodies (anti-H+/K+-ATPase, anti-intrinsic factor) attack gastric parietal cells in the fundus and body (antrum is spared - "Type A gastritis")
- Parietal cell destruction: Loss of both gastric acid (HCl) and intrinsic factor (IF)
- Achlorhydria → removes negative feedback on antral G cells → hypergastrinemia
- Absent IF → vitamin B12 cannot bind to the cubam receptor in the terminal ileum → B12 deficiency
- B12 deficiency → impaired DNA synthesis → megaloblastic changes in all rapidly dividing cells (bone marrow, GI mucosa)
- Result: Macrocytic megaloblastic anemia + GI mucosal atrophy (glossitis, diarrhea) + possible neurological complications (subacute combined degeneration of spinal cord)
Key Diagnostic Antibodies
- Anti-parietal cell antibodies (anti-H+/K+-ATPase): Present in ~80-90% of early PA; less specific
- Anti-intrinsic factor antibodies (IFA): More specific; Type I (blocking) prevents IF-B12 binding; Type II (binding) prevents cubam receptor attachment
- Both types of antibodies are present 2-3 decades before clinical disease appears
Why Elevated Gastrin is the Pathognomonic Clue
The elevated serum gastrin in this scenario directly points to pernicious anemia. As stated in Robbins: "The absence of acid production stimulates gastrin release, resulting in hypergastrinemia and hyperplasia of antral gastrin-producing G cells." This distinguishes PA from other causes of B12 deficiency (e.g., dietary deficiency, terminal ileal disease), where gastrin would be normal.
Associated Conditions
PA is strongly associated with other autoimmune diseases: Hashimoto thyroiditis, Type 1 diabetes mellitus, Addison disease, Graves disease (25% co-occurrence), and vitiligo.
Treatment
Intramuscular or high-dose oral vitamin B12 (cyanocobalamin or hydroxocobalamin) supplementation - lifelong, since the underlying autoimmune gastritis cannot be reversed.
Sources: Robbins, Cotran & Kumar Pathologic Basis of Disease (9780443264528), pp. 2117-2133; Goldman-Cecil Medicine (9780323930345), pp. 1192-1198; Henry's Clinical Diagnosis and Management by Laboratory Methods (9780323673204), pp. 2464-2495
This is a shared conversation. Sign in to Orris to start your own chat.