Learning Objective: By the end of this module, medical students will be able to identify key HLA subtypes and their associated autoimmune or inflammatory diseases, using mnemonics for rapid recall on USMLE Step 1.
Human Leukocyte Antigen (HLA) molecules play a crucial role in immune system recognition. Certain HLA subtypes are strongly associated with autoimmune diseases. Recognizing these patterns is essential for clinical reasoning and exam preparation.
HLA Subtypes and Disease Associations
| HLA Subtype | Associated Diseases | Mnemonic / Tip |
|---|---|---|
| B27 | Psoriatic arthritis, Ankylosing spondylitis, IBD-associated arthritis, Reactive arthritis | PAIR → Think of the 4 “PAIRed” diseases in spondyloarthropathies |
| DR3 | Type 1 Diabetes Mellitus (DM1), Systemic Lupus Erythematosus (SLE), Graves disease, Hashimoto thyroiditis, Addison disease | DM1: HLA-3 & -4 → 1 + 3 = 4, SL3 → SLE |
| DR4 | Rheumatoid arthritis, Type 1 Diabetes Mellitus, Addison disease | “There are 4 walls in 1 ‘rheum’ room” (RA mnemonic) |
Key Points
- B27 is primarily associated with spondyloarthropathies. Remember “PAIR” for Psoriatic arthritis, Ankylosing spondylitis, IBD arthritis, Reactive arthritis.
- DR3 and DR4 are linked to autoimmune endocrine disorders and type 1 diabetes.
- Mnemonics are extremely helpful for USMLE recall under timed conditions.
- HLA typing may be clinically relevant for diagnosis and risk assessment in autoimmune diseases.
