Autoimmune mechanisms in pernicious anaemia & thyroid disease

• We have reviewed current knowledge of the autoimmune pathogenesis of PA.
• We have explained the possible role of H. Pylori in the pathogenesis of autoimmunity.
• We have described the effect of immune complexes on the detection of B12 deficiency.
• We have described the relationship between PA and autoimmune thyroid disease.
• We have described mechanisms by which PA and thyroid disease cause elevated tHcy.

Pernicious anaemia (PA) and some types of thyroid disease result from autoimmune processes. The autoimmune mechanisms in these conditions have not been fully elucidated. This review discusses the autoimmune mechanisms involved in PA and how these affect diagnosis and disease progression. In addition to gastric antibodies, antibodies to the vitamin B12 binding protein transcobalamin which can result in high serum B12 levels are also addressed with regard to how they affect clinical practice. The role of autoimmune susceptibility is investigated by comparing PA to one of its most common comorbidities, autoimmune thyroid disease (AITD). Thyroid disease (although not exclusively AITD) and B12 deficiency are both also implicated in the pathology of hyperhomocysteinemia, an elevated homocysteine in plasma. Since hyperhomocysteinemia is a risk factor for cardiovascular occlusive disease, this review also addresses how thyroid disease in particular leads to changes in homocysteine levels.