Prevalence of adrenal antibodies in Addison's disease among north Indian Caucasians

OBJECTIVE The prevalence of antibodies in different organ-specific autoimmune diseases can vary depending on the racial group studied. Data on the prevalence of antibodies against steroidogenic enzymes in Addison's disease is available only for white Caucasians. We have evaluated the frequency of antibodies against adrenal cytoplasm, 21-hydroxylase, 17-alpha-hydroxylase and side-chain cleavage enzyme in a cohort of Indian patients with Addison's disease of idiopathic and granulomatous aetiology. DESIGN Study of all patients with Addison's disease on whom serum samples were available (84% of total), presenting to the Endocrinology Department in a teaching hospital in India, between 1990 and 1999. PATIENTS Thirty-eight patients with Addison's disease (19 idiopathic, 19 granulomatous). METHODS A radiobinding assay using in vitro transcribed and translated recombinant human S-35-labelled 21-hydroxylase, 17-alpha-hydroxylase and side-chain cleavage enzymes was utilized to detect the respective antibodies. Adrenal cytoplasmic antibodies were measured by indirect immunofluorescence on cryostatic sections of human adrenal cortex. RESULTS Of the 19 patients with idiopathic Addison's disease, adrenal cytoplasmic antibodies were present in five (26%) patients, while 21-hydroxylase antibodies were present in four (21%) subjects. The frequency of 21-hydroxylase antibodies was similar among patients with isolated idiopathic Addison's disease (3/13, 23%), and those associated with other organ-specific autoimmune diseases (1/6, 17%). 17-alpha-hydroxylase and side-chain cleavage antibodies were present in four (21%) and three (16%) patients, respectively. Overall, at least one of the three antibodies was present in eight (42%) subjects. All four female patients with premature ovarian failure had antibodies against 17-alpha-hydroxylase and/or side-chain cleavage enzyme. Two (11%) patients with granulomatous Addison's disease had adrenal antibodies. Of these, one patient with enlarged and calcified adrenal gland secondary to tuberculosis had a high titre of antibodies against all three steroidogenic enzymes. CONCLUSIONS Antibodies to 21-hydroxylase enzyme are less frequent in idiopathic Addison's disease in north Indians, when compared with other Caucasians. In contrast, the prevalence of 17-alpha-hydroxylase and side-chain cleavage enzyme antibodies is similar to those reported. High titre antibodies against steroidogenic enzymes may occasionally be present in patients with clinical evidence of tuberculous Addison's disease.