Malignant anaemia, also known as pernicious anaemia, is a medical condition that occurs due to vitamin B12 deficiency. The deficiency causes the body to produce abnormally large red blood cells, leading to anemia. Several synonyms can be used to refer to this condition, including Addisonian anaemia, Biermer's anaemia, and Macrocytic anaemia. These terms are commonly used in medical literature to describe the condition. Additionally, other terms related to the symptoms of malignant anaemia include fatigue, weakness, and pale skin. Early detection and treatment of malignant anaemia are crucial to prevent long-term complications such as nerve damage or gastrointestinal problems.