Autoimmune Pathology: NEET PG High-Yield Essentials
Autoimmune diseases are defined by the breakdown of self-tolerance. For NEET PG, mastery of these topics requires integrating three pillars: specific autoantibody profiles, HLA associations, and characteristic hypersensitivity mechanisms.
1. Essential Autoantibody Profiles
These markers are high-frequency targets for clinical vignette questions. Focus on the distinction between screening tests and highly specific markers.
| Autoantibody | Associated Disease | Key Clinical Pearl |
|---|---|---|
| Anti-dsDNA | SLE | Correlates with disease activity (lupus nephritis). |
| Anti-Smith (Sm) | SLE | Most specific marker for SLE. |
| Anti-Ro (SSA) / La (SSB) | Sjögren Syndrome | Risk of neonatal lupus and congenital heart block. |
| Anti-Scl-70 | Systemic Sclerosis (Diffuse) | Higher risk of pulmonary fibrosis. |
| Anti-Centromere | Systemic Sclerosis (CREST) | Better prognosis than the diffuse variant. |
| Anti-Jo-1 | Dermatomyositis | Associated with interstitial lung disease. |
| Anti-Mitochondrial (AMA) | Primary Biliary Cholangitis | Classic for middle-aged females with jaundice/pruritus. |
2. HLA & Genetic Associations
NEET PG examiners frequently utilize HLA patterns to test genetic risk architecture:
- HLA-B27: Ankylosing Spondylitis, Reactive Arthritis, Psoriatic Arthritis.
- HLA-DR3/DR4: Type 1 Diabetes Mellitus.
- HLA-DR4: Rheumatoid Arthritis.
- HLA-DQ2/DQ8: Celiac Disease (Strongest association).
- HLA-DR3: Graves ‘ disease, Addison’s disease.
3. Pathological “Must-Knows.”
Hypersensitivity Recap:
• Type II: Antibody-mediated tissue injury (Goodpasture, Rheumatic Fever, Myasthenia Gravis).
• Type III: Immune-complex mediated (SLE, Post-streptococcal glomerulonephritis, Serum sickness).
• Type IV: T-cell mediated/delayed (Contact dermatitis, TB test, Transplant rejection).
- Screening vs. Confirmation: ANA is the best screening test for SLE (high sensitivity). Anti-dsDNA and Anti-Sm are confirmatory (high specificity).
- Renal Pattern Recognition:
- Linear deposits on immunofluorescence = Goodpasture (Anti-GBM).
- Granular deposits = Immune complex diseases (SLE, PSGN).
- Granulomas: Sarcoidosis, Crohn disease, and berylliosis feature non-caseating granulomas. TB and fungal infections feature caseating (necrotic) granulomas.