1. Diagnostic tests
1.1. blood test
1.1.1. presence of antibodies against parietal cells and intrinsic factor
1.2. bone marrow aspiration
1.3. serologic studies
1.3.1. most commonly used
1.3.1.1. Measure methylmalonic acid and homocysteine levels
1.3.1.1.1. elevated early in disease
1.4. gastric biopsy
1.4.1. shows absence of hydrochloric acid
1.5. Schilling test
1.5.1. measures vitamin b12 absorption by administering radioactive B12 and measuring excretion in urine
1.5.1.1. low secretion indicates disease
2. Common findings
2.1. Develops slowly
2.1.1. Over 20-30 years
2.2. Early symptoms non-specfic
2.2.1. infections
2.2.2. mood swings
2.2.3. gastrointestinal, cardiac, renal issues
2.3. Classic symptoms of anemia
2.3.1. Fatigue, weakness, paresthesias of feet and fingers, difficulty walking, loss of appetite, abdominal pain, weight loss, sore tongue
2.4. Skin "lemon yellow" color
2.5. Hepatomegaly
2.6. Right sided heart failure
2.7. Splenomegaly
2.8. Neurological symptoms
2.8.1. ataxia, spasticity, loss of position and vibration sense, depression
3. Treatments
3.1. Replacement of vitamin b12
3.1.1. Injections administered weekly until replaced adequately
3.1.1.1. This is followed by monthly injections for life
3.1.1.2. Usually occurs in 5-6 weeks
3.2. No cure, requires maintenance therapy
4. Pathophysiological etiology
4.1. Absence of intrinsic factor
4.1.1. Transporter required for absorption of dietary B12
4.1.2. Normally secreted by gastric parietal cells
4.2. Autoantibodies aganist gastric H-K ATPase
4.2.1. Gastric submucosa infiltrated with inflammatory cells
4.2.1.1. Causes destruction of parietal and zymogenic cells
4.2.1.1.1. Replaced with mucous containing cells
4.2.1.1.2. Gastric mucosal atrophy occurs
4.2.1.1.3. Results in deficiency of gastric secretions including intrinsic factor
4.2.1.2. Mild chronic inflammation of stomach body
4.3. Autoimmune process may be initiated by Helicobacter pylori infection
5. Risk factors
5.1. > 30 years old
5.2. Northern European descent
5.3. Female
5.4. Alcohol
5.5. Smoking
6. Causative factors
6.1. Vitamin B12 deficiency
6.2. Congenital
6.3. Autoimmune process
6.3.1. Autoimmune gastritis
6.4. Chronic gastritis
6.4.1. Excessive alcohol or hot tea consumption
6.4.2. Smoking