MHCs, or major histocompatibility complexes, are molecules present on the surface of immune cells. HLA-DR is a type of MHC molecule. HLA-DR is a highly heterogeneous molecule in humans, and has many numerical variants, one of which is HLA-DR4.
The presence of HLA-DR4 in patients is associated with the development of many autoimmune diseases. The exact mechanism underlying this association is unknown, but the link between certain HLA molecules and autoimmune disease development is strong.
Rheumatoid Arthritis is associated with HLA-DR4 and HLA-DR1. This autoimmune disease causes symmetrical arthritis and joint swelling. To learn more about RA, visit our corresponding Picmonic.
The HLA-DR4 gene is associated with the development of type 1 diabetes, which is an autoimmune disease that attacks insulin-producing cells in the pancreas. For more information, visit the type 1 diabetes mellitus pathway.
Pemphigus Vulgaris is a type II hypersensitivity reaction directed against desmoglein 3 and 1 in desmosomes. This results in the loss of cell-to-cell adhesion in the epithelium. Symptoms include early pruritis followed by the development of widespread, flaccid bullae on the skin and oral mucosa.
Addison's Disease, or primary adrenal insufficiency, is characterized by the loss of adrenal function. This is most often due to autoimmune destruction of the glands. Patients will have symptoms related to deficiencies of hormones normally produced by the adrenal gland, including aldosterone, cortisol, and androgens. Additionally, increased levels of CRH will lead to hyperpigmentation.
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