Autoimmune Polyendocrine Syndromes¶
Chapter 401 | Part 12: Endocrinology and Metabolism · Part 12 – Endocrinology & Metabolism · Chapter 401
Key Clinical Points¶
- APS-1 (APECED) is an autosomal recessive disorder caused by AIRE gene mutations on chromosome 21, typically presenting in infancy.
- APS-1 diagnosis requires two of three major components: mucocutaneous candidiasis, hypoparathyroidism, and Addison's disease.
- APS-2 is a polygenic condition (HLA-DR3/DR4) with a 3:1 female-to-male ratio, typically presenting in adulthood (ages 20–60).
- APS-2 diagnosis requires two or more endocrine deficiencies: Addison's, thyroid disease, T1D, and primary hypogonadism.
- Anti-interferon α and ω antibodies identify nearly 100% of APS-1 cases.
- Addison's in both syndromes can be masked by primary hypothyroidism; treat adrenal insufficiency before thyroid hormone.
- IPEX is an X-linked recessive disorder caused by FOXP3 mutations, presenting with enteropathy, T1D, and skin disease in infancy.
- ICI-induced T1D is rapid-onset, permanent, and requires lifelong insulin; often associated with HLA-DR4.
- POEMS syndrome involves polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes; treated with rituximab, cyclophosphamide, and pulse steroids.
- Anti-21-hydroxylase antibodies confirm Addison's risk in both APS-1 and APS-2.
DEFINITION & CLASSIFICATION¶
• Autoimmune Polyendocrine Syndromes (APS): Group of disorders characterized by multiple autoimmune endocrine deficiencies. • APS-1 (APECED): • Full Name: Autoimmune polyendocrinopathy–candidiasis–ectodermal dystrophy. • Genetics: Autosomal recessive; mutations in the AIRE gene (chromosome 21). • Clinical Presentation: Early onset (infancy); includes mucocutaneous candidiasis, hypoparathyroidism, and Addison's disease. • APS-2: • Genetics: Polygenic; associated with HLA-DR3/DR4. • Clinical Presentation: Later onset (20–60 years); 3:1 female to male ratio. • Diagnostic Criteria: Presence of ≥ 2 endocrine deficiencies (Addison's, thyroid disease, T1D, or primary hypogonadism). • IPEX Syndrome: • Full Name: Immune dysregulation, polyendocrinopathy, enteropathy, and X-linked disease. • Genetics: X-linked recessive; mutations in the FOXP3 gene. • Clinical Presentation: Infancy onset; severe enteropathy, T1D, and skin disease.
EPIDEMIOLOGY¶
• APS-1: • Prevalence: Rare (<500 cases reported). • Age of Onset: Peaks in first or second decade of life. • Inheritance: Siblings of APS-1 patients should be considered at risk even if only one component is detected. • APS-2: • Prevalence: 1–2 per 100,000. • Sex Distribution: Females > males (ratio ≥ 3:1). • Age of Onset: Adulthood; peak incidence between 20 and 60 years. • Risk Factors: Strongly associated with HLA-DR3 and HLA-DR4.
ETIOLOGY & PATHOPHYSIOLOGY¶
• APS-1 (AIRE Mutation): • Mechanism: AIRE gene is expressed in medullary epithelial cells (mTECs) to control expression of tissue-specific self-antigens. • Pathology: Deletion leads to decreased self-antigen expression → autoreactive T cells avoid central deletion during maturation. • Genetic Diversity: >100 mutations identified; higher frequency in specific ethnic groups (e.g., Iranian Jews, Sardinians). • Non-classical Form: Autosomal dominant mutations in the PHD1 domain may lead to later onset and less aggressive disease. • APS-2 (HLA Association): • Primary Drivers: HLA-DR3 and HLA-DR4 are primary risk factors for Addison's. • Other Genetic Factors: • HLA-B8/DR3: Associated with IgA deficiency, dermatomyositis, alopecia, and hypophysitis. • MIC-A5.1: Strong association with Addison's disease. • PTPN22: Polymorphism in protein tyrosine sulfate; linked to T1D and Addison's. • CTLA4: Polymorphisms lead to decreased surface expression → increased T-cell activation → contributes to Addison's. • IL-2Rα: Variants linked to T1D and autoimmune thyroid disease. • IPEX (FOXP3 Mutation): • Mechanism: FOXP3 is essential for regulatory T cells (Treg) (CD4+CD25+FOXP3+). • Pathology: Lack of FOXP3 → profound deficiency of Treg population → loss of peripheral tolerance → rampant autoimmunity. • Other Genetic Associations: • Wolfram Syndrome (DIDMOAD): WFS1 gene mutation; affects calcium homeostasis; associated with T1D, thyroiditis, and celiac disease. • Down Syndrome: Associated with T1D, thyroiditis, and celiac disease. • Turner Syndrome: Increased risk for thyroid disease and celiac disease.
CLINICAL FEATURES¶
• APS-1 Features: • Mucocutaneous Candidiasis: Nearly always present; often first manifestation; affects mouth/nails more than skin/esophagus. • Hypoparathyroidism: Found in >85% of cases. • Addison's Disease: Found in nearly 80% of cases. • Other Endocrine: T1D (23%), autoimmune thyroid disease (18%), gonadal failure (70% females, 25% males). • Non-endocrine: Alopecia (40%), vitiligo (26%), malabsorption (18%), pernicious anemia (31%), IgA deficiency. • Specific Findings: Hypoplasia of dental enamel (77%); hyperpigmentation; tetany. • APS-2 Features: • Addison's Disease: 50–70% prevalence. • Thyroid Disease: Graves' or autoimmune thyroiditis (15–69%). • T1D: 40–50% prevalence. • Hypogonadism: Included in defining criteria. • Associated Conditions: Celiac disease (3–15%), myasthenia gravis, vitiligo, alopecia, serositis, pernicious anemia. • ICI-Induced Endocrine Autoimmunity: • Mechanism: Blockade of PD-1, PD-L1, or CTLA-4 → loss of immune regulation → autoimmunity. • T1D Presentation: Rapid onset; presents with DKA; permanent; requires lifelong insulin. • Thyroid/Hypophysitis: Occur in 10% and 1–2% of patients receiving anti-CD3 antibodies, respectively. • POEMS Syndrome: • Clinical Triad: Polyneuropathy, organomegaly, endocrinopathy (50% DM, 70% gonadal failure). • Other Features: M-protein with sclerotic bone lesions; hepatosplenomegaly; hyperpigmentation. • Course: Median survival <3 years without treatment; some cases show spontaneous remission. • Table 401-1 & 401-2 Summary: • APS-1 is associated with candidiasis, hypoparathyroidism, and IgA deficiency. • APS-2 is associated with myasthenia gravis, vitiligo, and pernicious anemia. • Table 401-3 Highlights: • Addison's: Requires Sodium, potassium, ACTH, cortisol, and 21/17-hydroxylase antibodies. • Hypoparathyroidism: Requires Serum calcium, phosphate, PTH. • T1D: Requires Glucose, HbA1c, and autoantibodies (GAD65, IA-2, ZnT8). • Celiac Disease: Requires Transglutaminase antibodies and biopsy.
DIFFERENTIAL DIAGNOSIS¶
• APS-1 Differential: • Mucocutaneous Candidiasis: Other immunodeficiencies. • Hypoparathyroidism: Genetic causes, parathyroidectomy. • Addison's Disease: Adrenal hemorrhage, tuberculosis, other autoimmune causes. • Key Discriminator: Anti-interferon α and anti-interferon \omega antibodies (identify ≈100% of APS-1). • APS-2 Differential: • Addison's Disease: Adrenal hemorrhage, tuberculosis. • Thyroid Disease: Iodine-induced, drug-induced. • T1D: Idiopathic, other genetic syndromes. • Hypogonadism: Kallmann syndrome. • IPEX Differential: • Other causes of early-onset T1D, severe enteropathy, or skin disease. • Key Discriminator: FOXP3 mutation confirms IPEX.
DIAGNOSTIC APPROACH¶
- Initial Clinical Assessment: • Identify core symptoms (e.g., candidiasis, hypoparathyroidism, adrenal insufficiency). • Assess for non-endocrine signs: hyperpigmentation, vitiligo, alopecia, tetany.
- Laboratory Screening (Standard): • CMP, Phosphorus, Magnesium. • TSH, ACTH (morning), HbA1c. • CBC with peripheral smear (look for Howell-Jolly bodies → indicates asplenism).
- Specific Antibody Testing: • APS-1 Identification: Test for anti-interferon α and anti-interferon \omega (high specificity for APS-1). • Addison's Confirmation: • Test for 21-hydroxylase antibodies. • Test for 17-hydroxylase antibodies (more common in APS-1 associated adrenal insufficiency). • Thyroid Assessment: TSH, thyroid peroxidase/thyroglobulin antibodies, anti-TSH receptor antibodies.
- Genetic Testing: • Perform AIRE gene analysis to identify mutations in suspected APS-1 cases. • Perform FOXP3 mutation analysis for suspected IPEMS.
- Specialized Evaluations based on findings: • Howell-Jolly bodies detected → Ultrasound of spleen. • Suspected Celiac Disease → Transglutaminase antibodies and small intestine biopsy. • Suspected Malabsorption → Physical exam, anti-IL-17, and anti-IL-22 antibodies.
MANAGEMENT & TREATMENT¶
- General Principles: • Identify all endocrine components early. • Critical Sequence: If both adrenal insufficiency and primary hypothyroidism are present, treat adrenal insufficiency first before starting thyroid hormone.
- Addison's Disease Management: • Confirm with 21-hydroxylase antibodies. • If positive → initiate glucocorticoid/mineralocorticoid replacement.
- Type 1 Diabetes (T1D): • Standard T1D: Insulin therapy based on clinical need. • ICI-induced T1D: Requires lifelong exogenous insulin; onset is rapid with DKA.
- POEMS Syndrome Management: • Target B-lymphocytes: Rituximab, cyclophosphamide, and pulse steroids.
- Hypoparathyroidism: • Manage based on serum calcium, phosphate, and PTH levels.
- Celiac Disease: • If transglutaminase antibodies are positive → initiate gluten-free diet/management.
COMPLICATIONS & PROGNOSIS¶
• APS-1 Prognosis: • Chronic mucocutaneous candidiasis is often not responsive to treatment. • Risk of squamous cell carcinoma in areas of chronic oral candidiasis (atrophic areas). • POEMS Syndrome Prognosis: • Median survival <3 years without intervention. • Potential for severe hypoglycemia due to partial insulin receptor activation by antibodies.
SPECIAL POPULATIONS¶
• Genetic Considerations: • Siblings of APS-1 patients must be screened even if only one component is present. • Identification of AIRE mutations allows for early identification of risk in family members. • Immune Checkpoint Inhibitors (ICIs): • Patients receiving anti-PD-1, anti-PD-L1, or anti-CTLA-4 must be monitored for: • T1D (1–2% incidence), Thyroid disease (10%), Hypophysitis, and Adrenal insufficiency. • ICI-induced T1D is characterized by rapid onset and high association with HLA-DR4.
KEY PEARLS & HIGH-YIELD POINTS¶
• Rule of Two: APS-1 requires 2 of 3 (Candidiasis, Hypoparathyroidism, Addison's); APS-2 requires 2+ endocrine deficiencies. • The "Addison's Rule": Always treat adrenal insufficiency before thyroid hormone to avoid precipitating an adrenal crisis. • Antibody Specificity: Anti-interferon α/\omega are highly specific for APS-1; anti-21-hydroxylase is the standard for Addison's. • Age/Sex Distinction: APS-1 = Infancy/Any sex; APS-2 = Adulthood/Female predominance. • POEMS Treatment: Rituximab and cyclophosphamide are key agents for B-cell targeted therapy.
Reference Tables¶
TABLE 401-1 Disease Associations with Autoimmune Polyendocrine Syndromes¶
Harrison's 22e, p.3089
| AUTOIMMUNE POLYENDOCRINE SYNDROME TYPE 1 |
AUTOIMMUNE POLYENDOCRINE SYNDROME TYPE 2 |
OTHER AUTOIMMUNE POLYENDOCRINE DISORDERS |
|---|---|---|
| Endocrine | Endocrine | IPEX (immune dysfunction polyendocrinopathy X-linked) |
| Addison’s disease | Addison’s disease | Thymic tumors |
| Hypoparathyroidism | Type 1 diabetes | Anti-insulin receptor antibodies |
| Hypogonadism | Graves’ disease or autoimmune thyroiditis |
POEMS syndrome |
| Graves’ disease or autoimmune thyroiditis |
Hypogonadism | Insulin autoimmune syndrome (Hirata’s syndrome) |
| Type 1 diabetes | Adult combined pituitary hormone deficiency (CPHD) with anti-Pit1 autoantibodies |
|
| Kearns-Sayre syndrome | ||
| DIDMOAD syndrome | ||
| Nonendocrine Celiac disease, dermatitis herpetiformis Pernicious anemia Vitiligo Alopecia Myasthenia gravis IgA deficiency Parkinson’s disease Idiopathic thrombocytopenia |
TABLE 401-2 Comparison of APS-1 and¶
Harrison's 22e, p.3089
| APS-1 | APS-2 |
|---|---|
| Early onset: infancy | Later onset |
| Equivalent sex distribution | Females > males affected |
| Not HLA associated for entire syndrome, some specific component risk |
DR3/DR4 associated; other HLA class III gene associations noted |
| Autoantibodies to specific target organs |
Autoantibodies to specific target organs |
| Mucocutaneous candidiasis | Association with other nonendocrine immunologic disorders like myasthenia gravis and idiopathic thrombocytopenic purpura |
TABLE 401-3 Clinical Features and Recommended Follow-Up for APS-1 and¶
Harrison's 22e, p.3090
| COMPONENT DISEASE | RECOMMENDED EVALUATION |
|---|---|
| APS-1 | |
| Addison’s disease | Sodium, potassium, ACTH, cortisol, 21- and 17-hydroxylase autoantibodies |
| Diarrhea | History |
| Ectodermal dysplasia | Physical examination |
| Hypoparathyroidism | Serum calcium, phosphate, PTH |
| Hepatitis | Liver function tests |
| Hypothyroidism/Graves’ disease | TSH; thyroid peroxidase and/or thyroglobulin autoantibodies and anti-TSH receptor Ab |
| Male hypogonadism | FSH/LH, testosterone |
| Malabsorption | Physical examination, anti-IL-17 and anti-IL-22 autoantibodies |
| Mucocutaneous candidiasis | Physical examination, mucosal swab, stool samples |
| Obstipation | History |
| Ovarian failure | FSH/LH, estradiol |
| Pernicious anemia | CBC, vitamin B levels 12 |
| Splenic atrophy | Blood smear for Howell-Jolly bodies; platelet count; ultrasound if positive |
| Type 1 diabetes | Glucose, hemoglobin A , diabetes-associated 1c autoantibodies (insulin, GAD65, IA-2, ZnT8) |
| APS-2 | |
| Addison’s disease | 21-Hydroxylase autoantibodies, ACTH stimulation testing if positive |
| Alopecia | Physical examination |
| Autoimmune hyper- or hypothyroidism |
TSH; thyroid peroxidase and/or thyroglobulin autoantibodies, anti-TSH receptor Ab |
| Celiac disease | Transglutaminase autoantibodies; small intestine biopsy if positive |
| Cerebellar ataxia | Dictated by signs and symptoms of disease |
| Chronic inflammatory demyelinating polyneuropathy |
Dictated by signs and symptoms of disease |
| Hypophysitis | Dictated by signs and symptoms of disease, anti-Pit1 autoantibody |
| Idiopathic heart block | Dictated by signs and symptoms of disease |
| IgA deficiency | IgA level |
| Myasthenia gravis | Dictated by signs and symptoms of disease, antiacetylcholinesterase Ab |
| Myocarditis | Dictated by signs and symptoms of disease |
| Pernicious anemia | Anti–parietal cell autoantibodies |
| CBC, vitamin B levels if positive 12 |
|
| Serositis | Dictated by signs and symptoms of disease |
| Stiff man syndrome | Dictated by signs and symptoms of disease |
| Vitiligo | Physical examination, NALP-1 polymorphism |
TABLE 401-4 APS-2 and Other Polyendocrine Disorder Associations DISEASE Graves’ disease Myasthenia gravis Anti-insulin…¶
Harrison's 22e, p.3091
| DISEASE | HLA ASSOCIATION | INITIATING FACTOR | MECHANISM | AUTOANTIGEN |
|---|---|---|---|---|
| Graves’ disease | DR3 | Iodine Anti-CD52 |
Antibody | TSH receptor |
| DR3, DR7 | Thymoma Penicillamine |
Antibody | ||
| Anti-insulin receptor | ? | SLE or other autoimmune disease | Antibody | Insulin receptor |
| ? | ? | Antibody | ||
| Insulin autoimmune syndrome | DR4, DRB1*0406 | Methimazole Sulfhydryl-containing drugs |
Antibody | Insulin |
| DQ2/DQ8 | Gluten diet | T cell | ||
| Type 1 diabetes | DR3/DR4 DQ2/DQ8 |
? Congenital rubella |
T cell | Insulin, GAD65, IA-2, ZnT8, IGRP |
| DR3/DR4 DRB1*0404 |
Unknown | T cell | ||
| Thyroiditis | DR3/DQB10201 DQA10301 |
Iodine Interferon α |
T cell | Thyroglobulin Thyroid peroxidase |
| ? | ? | T cell | ||
| Vitiligo | ? | Melanoma Antigen Immunization |
? | Melanocyte |
| DQA1*0301 | ? | ? | ||
| Hypophysitis | ? | Pit-1, TDRD6 | ? | Pituitary, Pit-1 |