HLA-DR3 antigen linkage in patients with hypertrophic obstructive cardiomyopathy.

In order to investigate if genetic factors could be involved in the pathogenesis of hypertrophic obstructive cardiomyopathy, we determined HLA-A, HLA-B, HLA-C, and HLA-DR specificities in 12 Italian patients affected with the disease and in healthy family members of one of them. HLA-DR3 was found in 50% of patients as compared to 17.1% of normal control subjects (p = 0.023, relative risk = 4.82). The two relatives also had HLA-DR3 antigen and, in addition, showed equivocal signs of hypertrophy at echocardiographic examination. Thus hypertrophic obstructive cardiomyopathy is associated with genes in the HLA-DR region, and immunogenetic factors could be involved in the pathogenesis of the disease. Furthermore, the minimal target organ abnormalities in "healthy" relatives could represent a subclinical stage of the disease.