Pernicious anaemia, also known as Addison's anaemia, refers to a type of anaemia that arises due to a lack of vitamin B12 in the body. This condition can lead to a range of symptoms, including fatigue, weakness, numbness, tingling, and difficulty walking. While pernicious anaemia is the most commonly used term to describe this condition, there are several other synonyms that can be used. These include Megaloblastic anaemia, Biermer's anaemia, or Addisonian anemia. No matter what it's called, prompt treatment and management of symptoms are necessary for individuals who are diagnosed with this condition.