DR4 is associated with extraarticular[2] rheumatoid arthritis,[3] hydralazine-induced female systemic lupus erythematosus,[4] pemphigoid gestationis,[5] pemphigus foliaceus,[6] obstructive hypertrophic cardiomyopathy,[7] IgA nephropathy,[8] 'shared syndrome'-systemic sclerosis/rheumatoid arthritis[9] and polymyalgia rheumatica.
[16] HLA-DRB1*04:01 gene variant is found three times more often in asymptomatic carriers of SARS-CoV-2 than in patients with symptoms of COVID-19.
This variant of the gene is more common in northern and western Europe, which means that people of European descent are more likely to be asymptomatic carriers that can transmit the disease to more susceptible populations.
[29] DR4-DQ8 is a risk factor for papillary thyroid carcinoma,[30] juvenile diabetes, coeliac disease and rheumatoid arthritis.
[37] DRB1*01:01/*04:04 and *01:01/*04:01 increases risk of mortality in rheumatoid arthritis, with ischemic heart disease and smoking.