Autoimmunity predominates in a large South African cohort with addison's disease of mainly European descent despite long-standing disease and is associated with HLA DQB*0201

Abstract

Objective We sought to determine whether autoimmunity is the predominant cause of Addison's disease in South Africa and whether human leucocyte antigen (HLA) DQ association exists. Design We compiled a national registry of patients from primary care, referral centres and private practices. Patients A total of 144 patients, 94 of European descent, 34 Mixed Ancestry, 5 Asian and 11 Black Africans (mean age 45·9 years, range 2·7-88 years; mean duration of disease 13·1 years, range 0-50 years) and controls were matched for gender and ethnicity. All potential causes were investigated. Results Fifty one per cent of cases (74 patients) were autoimmune in aetiology. Either 21-hydroxylase autoantibodies (72 patients, 50% of entire patient group) or adrenocortical autoantibodies (35 patients, 24%) were present, while 23% of patients had both. None of the Asian (n = 5) or Black (n = 11) patients had evidence of autoimmune disease. Overall 8% of patients had tuberculosis, 4% adrenoleucodystrophy, 1% adrenocorticotrophic hormone resistance syndrome and 6% X-linked adrenal hypoplasia. In those with autoimmune disease primary hypothyroidism (47%), premature ovarian failure (8%) and type 1 diabetes (7%) were the most prevalent accompanying autoimmune conditions. HLA DQB1*0201 alleles predominated in the autoimmune group (DQB1*0201: 65%vs 43% of controls P = 0·017) with the *0201/*0302 heterozygous genotype being the most prevalent (28%vs 8%P = 0·02). Conclusions While autoimmunity accounts for at least half of patients with Addison's disease in South Africa and is associated with HLA DQB1*0201, none of the Black Africans or Asians in this cohort had adrenal autoantibodies. Moreover, 21-hydroxylase autoantibodies were detectable in a higher proportion than adrenocortical autoantibodies, especially in those patients with a long history after disease onset. © 2010 Blackwell Publishing Ltd.