Glossitis of the tongue in iron deficiency anemia has been described as diffuse or patchy atrophy with tenderness or burning. One cause of iron deficiency anemia is sideropenic dysphagia (Plummer–Vinson or Paterson–Brown–Kelly syndrome) which is also characterized by esophageal webbing and dysphagia. Pernicious anemia is usually caused by autoimmune destruction of gastric parietal cells. Parietal cells secrete intrinsic factor which is required for the absorption of vitamin B12. Vitamin B12 deficiency results in megaloblastic anemia and may present as glossitis. The appearance of the tongue in vitamin B12 deficiency is described as "beefy" or "fiery red and sore". There may be
The Canon of Medicine anatomy, and physiology. The book explains the causes of health and disease. Avicenna believed that the human body cannot be restored to health unless the causes of both health and disease are determined. He defined medicine ("tibb") as follows: Avicenna begins part one by dividing theoretical medicine and medical practice. He describes what he says are the "four causes" of illness, based on Aristotelian philosophy: The material cause, the efficient cause, the formal cause, and the final cause: Avicenna's thesis on the elements of the cosmos is described by Gruner as "the foundation of the whole "Canon"". Avicenna insists here