Pernicious Anaemia (B12) Flashcards
what is the definition of B12 anaemia?
Low B12 (normal 197 –771ng/l), Type of macrocytic anaemia
what is the epidemiology of B12 anaemia?
- The disease is common in the elderly (over 60)
- Seen in all races but more common in fair-haired, blue eyed individuals and those who have blood group A
- More common in FEMALES than males
- There is also an association with other autoimmune disease such as thyroid disease and Addison’s disease
what is the aetiology of B12 anaemia?
Pernicious anaemia (autoimmune gastric atrophy; loss of intrinsic factor production) gastrectomy/ ileal resection vegan diet bacterial overgrowth oral contraceptives hypochloridia Recreational nitric oxide use
what are the risk factors for B12 anaemia?
- Veganism (exclusively found in meat and dairy products)
- Elderly
- Female
- Fair-haired, blue eyes
- Blood group A
- Thyroid and Addison’s disease
what is the pathophysiology of B12 anaemia?
Pernicious anaemia is an AUTOIMMUNE DISORDER in which the parietal cells of the stomach are attacked resulting in atrophic gastritis and the loss of intrinsic factor production and thus vitamin B12 malabsorption
Thus in B12 deficiency there is an impairment of DNA synthesis resulting in delayed nuclear maturation resulting in large RBCs as well as decreased RBC production in the bone marrow
- This DNA impairment will affect all cells, but bone marrow is most affected since it’s the most active in terms of cell division
what are the key presentations of B12 anaemia?
Onset is insidious with progressively increasing symptoms of anaemia, lemony yellow coloued skin (due to pallor and jaundice), red sore tongue, neurological features
what are the signs of B12 anaemia?
Tachycardia, anorexia, mild jaundice
Neurological - dementia, optic atrophy
what are the symptoms of B12 anaemia?
Fatigue, headache, dyspnea, palpitations, pallor, yellowy skin, red sore tongue, ulcerations on corners of mouth
Neurological - paresthesia (symmetrical burning in fingers and toes), loss of proprioception, weakness and ataxia, paraplegia, hallucinations
what are the first line investigations for B12 anaemia?
Blood count & film:
• Typical of megaloblastic anaemia
• RBC’s are MACROCYTIC
• Peripheral film shows oval macrocytes (large RBC’s) with hypersegmented neutrophil polymorphs with six or more lobes in the nucleus
what are the gold standard investigations for B12 anaemia?
- Serum bilirubin may be raised as a result of ineffective erythropoiesis resulting in increased RBC breakdown
- Serum B12 is low
- Hb is low
- Reticulocyte count is LOW
- Intrinsic factor antibodies - DIAGNOSTIC but lower sensitivity i.e. not present in all patients
what are the differential diagnoses for B12 anaemia?
Must differentiate from the other cause of megaloblastic anaemia - folate deficiency
- Differentiate from other causes of B12 deficiency
- Any disease in the terminal ileum or bacterial overgrowth in the small bowel can result in B12 deficiency
- Gastrectomy
how is B12 anaemia managed?
• In combined B12 and folate deficiency, ensure B12 started before folate
- If not pernicious anaemia then treat cause
- If a low B12 is due to malabsorption then injections are required
- If cause is dietary then give oral B12
- Replenish B12 stores by giving IM HYDROXOCOBALAMIN
how is B12 anaemia monitored?
Regular blood tests after medication started
what are the complications of B12 anaemia?
vision problems
memory loss
pins and needles (paraesthesia)
loss of physical coordination (ataxia), which can affect your whole body and cause difficulty speaking or walking
damage to parts of the nervous system (peripheral neuropathy), particularly in the legs
what is the prognosis of B12 anaemia?
With treatment, recovery in 6-12 months, untreated causes complications
