Master HLA-DR3 Associations with Picmonic for Medicine

MHCs, or major histocompatibility complexes, are molecules that are critical for the immune system. They enable the body to identify and respond to pathogens. MHCs are found on the surface of every cell and are crucial for presenting antigens (foreign substances) to T cells, resulting in the initiation of an immune response. There are two classes of MHCs: MHC-I and MHC-II. HLA-DR is a type of MHC-II molecule. HLA-DR is highly heterogeneous in humans and has many numerical variants, one of which is HLA-DR3.

The presence of HLA-DR3 in patients is associated with an increased risk of developing many autoimmune diseases. The exact mechanism underlying this association is unknown, but the link between certain HLA molecules and the development of autoimmune diseases is strong.

The HLA-DR3 gene is associated with type 1 diabetes mellitus, which is an autoimmune disease which attacks insulin producing cells in the pancreas. Patients with HLA-DR3 have about a six-fold increase in the risk of the development of type 1 diabetes mellitus.

Systemic Lupus Erythematosus (SLE) is associated with HLA-DR3. This disease is linked not only to HLA-DR3 but also to HLA-DR2. SLE is a complex, multisystem disease that mostly involves arthralgias, photosensitivity, and the destruction of all three blood lines: red blood cells, white blood cells, and thrombocytes. But SLE can cause many more clinical manifestations

Hashimoto's thyroiditis is linked to both HLA-DR3 and HLA-DR5. This disease results from self-reactive T-cells that target and destroy thyroid peroxidase. The main manifestation of Hashimoto's thyroiditis is hypothyroidism, but in the beginning, it can present with a transient hyperthyroid phase where pre-formed thyroid hormones are released into the blood.

The presence of HLA-DR3 increases the likelihood of developing Graves' disease. As with other autoimmune diseases and disorders associated with HLA-DR3, the exact mechanism underlying this association is unknown. Graves' disease presents with a diffusely enlarged thyroid and hyperthyroidism.

Addison’s Disease, or primary adrenal insufficiency, is associated with the presence of HLA-DR3. This condition results from an autoimmune attack on the cells of the adrenal cortex. Patients typically present with fatigue, weight loss, orthostatic hypotension, hyperpigmentation, and/or electrolyte abnormalities.