['Polyglandular failure or autoimmunity (PGA) involves at least two endocrine diseases. Several genes may play a role in its etiology. This study analyzed 1) whether HLA-DRB1, HLA-DQB1, and MHC class I chain-related gene A (MICA) polymorphisms are associated in PGA and 2) whether PGA patients display stronger associations with these immune genes than patients with monoglandular autoimmunity (MGA).', 'Association study.', 'HLA-DRB1, HLA-DQB1, and MICA alleles were analyzed in 73 patients with PGA, 283 with MGA, and 206 healthy controls. The HLA-DRB1 and HLA-DQB1 polymorphisms were determined with PCR-amplified DNA being hybridized with PCR-sequence-specific oligonucleotide probes. MICA microsatellites were typed by PCR amplification and fragment size analysis on a DNA sequencer.', 'HLA-DRB1*03 was strongly increased in patients with PGA (50.7%) versus both controls (21.8%, P(c)<0.0001; RR=2.32, 95% CI=1.62-3.33) and MGA (11.4%, P(c)<0.0001). HLA-DRB1*03 was highly prevalent in PGA patients with early versus late disease onset (P<0.05, logistic regression analysis). HLA-DRB1*04 allele carriers were more present in PGA versus controls (53.4% vs 22.4%, P(c)<0.0001, RR=2.38, 95% CI=1.68-3.38). Further, HLA-DQB1*02 was increased in PGA versus controls (P(c)<0.01), whereas HLA-DQB1*06 was decreased (P(c)<0.001). Patients with PGA showed more MIC A5.1 and less MIC A6 allele carriers than controls (NS). Presence of the MIC A5.1 allele was not associated with the HLA-DRB1*03 or HLA-DQB1 alleles.'] Is early onset of polyglandular failure associated with HLA-DRB1*03?