Reflex sympathetic dystrophy (RSD) is a relatively common disabling disorde
r of unknown pathophysiology. From a cohort of 52 patients, carefully selec
ted to fulfill the recently formulated diagnostic criteria for RSD, venous
blood samples were taken for typing of class I and II major histocompatibil
ity antigens. The frequency of HLA-DQ1 was found to be significantly increa
sed compared with control frequencies. The association provides an indicati
on for an organic basis of RSD.