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Autoimmune Polyendocrine Syndromes
🧬 Type 1 Autoimmune Polyglandular Syndrome (APS-1)
- Inheritance: Autosomal recessive mutations of the AIRE (Autoimmune Regulator) gene on chromosome 21.
- Pathophysiology: AIRE is critical for central tolerance in the thymus – its failure → autoreactive T cells escape deletion → multi-organ autoimmunity.
- Clinical Triad (classic 👑):
- 🟠 Addison’s disease (primary adrenal insufficiency).
- 🍄 Chronic mucocutaneous candidiasis (defective IL-17 immunity).
- ⚪ Hypoparathyroidism.
- Other associations: hypogonadism, pernicious anaemia, autoimmune thyroid disease, chronic active hepatitis, vitiligo, alopecia.
- Usually presents in childhood or adolescence.
🧬 Type 2 Autoimmune Polyglandular Syndrome (APS-2)
- Inheritance: Polygenic, strongly linked to HLA-DR3 and HLA-DR4.
- Much more common than APS-1; onset typically in adulthood (20–40 years).
- Clinical Triad:
- 🟠 Addison’s disease (always present).
- 💉 Type 1 diabetes mellitus (≈20%).
- 🦋 Autoimmune thyroid disease (hypothyroidism or Graves’).
- Other associations: primary hypogonadism, vitiligo, alopecia, pernicious anaemia, chronic atrophic gastritis, coeliac disease, dermatitis herpetiformis.
⚖️ Key Differences Between APS-1 and APS-2
| Feature | APS-1 | APS-2 |
|---|---|---|
| Genetics | Autosomal recessive, AIRE gene mutation | Polygenic, HLA-DR3/DR4 linked |
| Onset | Childhood/adolescence | Adulthood (20–40 yrs) |
| Classic triad | Addison’s + candidiasis + hypoparathyroidism | Addison’s + T1DM + thyroid disease |
| Other features | Hypogonadism, pernicious anaemia, hepatitis, vitiligo, alopecia | Vitiligo, alopecia, pernicious anaemia, coeliac, dermatitis herpetiformis |
📚 Teaching Pearls
- APS-1 is sometimes called APECED (Autoimmune Polyendocrinopathy, Candidiasis, Ectodermal Dystrophy).
- In exams: Think “Addison’s + 2 other autoimmune conditions” → suspect APS.
- Patients require life-long hormone replacement + screening for new autoimmune diseases.
- Family history and HLA typing can guide risk in APS-2.
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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