Anti-intrinsic factor antibodies in systemic lupus erythematosus

As the co-existence of pernicious anaemia (PA) and systemic lupus erythematosus (SLE) has been repeatedly reported, we have investigated the presence of anti-intrinsic factor antibodies (IFAb), the immunological hallmark of PA, in patients diagnosed with SLE. Serum cobalamin levels and IFAb were determined in 30 women diagnosed with SLE as well as in 45 controls. Cobalamin levels were low in 7/30 patients. IFAb were detected in 3/30 sera from patients but in none of the control sera. The presence of IFAb was associated with a low cobalamin concentration, anaemia and macrocytosis in only one patient. There was no evident relationship between the presence of IFAb and serological markers of SLE. We conclude that IFAb may appear in SLE patients, although the cobalamin deficiency described in SLE seems to be due to the presence of IFAb in only a minority of cases.