Autoimmune Polyendocrine Syndromes¶
Chapter 401 | Part 12: Endocrinology
KEY CLINICAL POINTS¶
- APS-1 (APECED) is an autosomal recessive disorder caused by AIRE gene mutations, characterized by Addison’s disease, hypoparathyroidism, and mucocutaneous candidiasis.
- APS-2 is a polygenic disorder linked to HLA-DR3/DR4, presenting with autoimmune endocrinopathies like Addison’s disease, T1D, and thyroiditis.
- IPEX syndrome is an X-linked disorder caused by FOXP3 mutations, presenting with enteropathy, T1D, and skin disease in infancy.
- Diagnosis relies on clinical criteria, autoantibody detection, and genetic testing (AIRE for APS-1, HLA for APS-2).
- Management includes hormone replacement, immunosuppression, and targeted therapies for individual component disorders.
1. DEFINITION & OVERVIEW¶
Autoimmune polyendocrine syndromes (APS) are rare disorders characterized by multiple autoimmune endocrinopathies. APS-1 (APECED) is autosomal recessive with AIRE gene mutations, while APS-2 is polygenic with HLA associations. IPEX syndrome is X-linked and involves immune dysregulation.
Table 401-1 Disease Associations with Autoimmune Polyendocrine Syndromes¶
| AUTOIMMUNE POLYENDOCRINE SYNDROME TYPE 1 | AUTOIMMUNE POLYENDOCRINE SYNDROME TYPE 2 | OTHER AUTOIMMUNE POLYENDOCRINE DISORDERS |
|---|---|---|
| Endocrine | Endocrine | IPEX (immune dysfunction 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 | Nonendocrine | Congenital rubella associated with thyroiditis and/or diabetes |
| AUTOIMMUNE POLYENDOCRINE SYNDROME TYPE 1 | AUTOIMMUNE POLYENDOCRINE SYNDROME TYPE 2 | OTHER AUTOIMMUNE POLYENDOCRINE DISORDERS |
|---|---|---|
| Celiac disease, dermatitis herpetiformis | Celiac disease, dermatitis herpetiformis | |
| Pernicious anemia | Pernicious anemia | |
| Vitiligo | Vitiligo | |
| Alopecia | Alopecia | |
| Myasthenia gravis | Myast, IgA deficiency | |
| Idiopathic thrombocytopenia | Idiopathic thrombocytopenia | |
| Mucocutaneous candidiasis | Mucocutaneous candidiasis |
Table 401-2 Comparison of APS-1 and APS-2¶
| APS-1 | APS-2 |
|---|---|
| Early onset: infancy | Later onset |
| Siblings often affected | Multigenerational |
| Mucocutaneous candidiasis | Celiac disease, dermatitis herpetiformis |
| Chronic active hepatitis | Pernicious anemia |
| Vitiligo | Alopecia |
| Autoantibodies to type 1 interferons | No autoantibodies to cytokines |
| Asplenism | Myasthenia gravis |
| Ectodermal dysplasia | IgA deficiency |
| Autoantibodies to specific target organs | Autoantibodies to specific target organs |
1.1 Subtopic¶
APS-1 (APECED) presents with mucocutaneous candidiasis, hypoparathyroidism, and Addison’s disease. APS-2 involves autoimmune endocrinopathies like T1D, Addison’s disease, and thyroiditis. IPEX syndrome is a rare X-linked disorder with enteropathy, T1D, and skin disease.
2. EPIDEMIOLOGY¶
APS-1 is rare (<500 cases reported), with higher frequency in Finns, Iranian Jews, Sardinians, Norwegians, and Irish. APS-2 has a prevalence of 1–2 per 100,000, with a female predominance (3:1 ratio). IPEX syndrome is extremely rare, with most cases fatal in infancy.
Table 401-4 APS-2 and Other Polyendocrine Disorder Associations¶
| DISEASE | HLA ASSOCIATION | INITIATING FACTOR | MECHANISM | AUTOANTIGEN |
|---|---|---|---|---|
| Graves’ disease | DR3 | Iodine | Antibody | TSH receptor |
| Myasthenia gravis | DR3, DR7 | Thymoma | Antibody | Acetylcholine receptor |
| Anti-insulin receptor | ? | SLE or other autoimmune disease | Antibody | Insulin receptor |
| Hypoparathyroidism | ? | ? | Antibody | Cell surface inhibitor |
| DISEASE | HLA ASSOCIATION | INITIATING FACTOR | MECHANISM | AUTOANTIGEN |
|---|---|---|---|---|
| Insulin autoimmune syndrome | DR4, DRB1*0406 | Methimazole | Antibody | Insulin |
| Celiac disease | DQ2/DQ8 | Gluten diet | T cell | Transglutaminase |
| Type 1 diabetes | DR3/DR4 | ? | T cell | Insulin, GAD65, IA-2, ZnT8, IGRP |
| Thyroiditis | DR3/DQB1*0201 | Iodine | T cell | Thyroglobulin |
| Pernicious anemia | ? | ? | T cell | Intrinsic factor |
| Vitiligo | ? | Melanoma | Antigen immunization | Melanocyte |
| Hypophysitis | ? | Pit-1, TDRD6 | ? | Pituitary, Pit-1 |
2.1 Risk Factors¶
APS-1: Autosomal recessive inheritance, AIRE gene mutations. APS-2: Polygenic, HLA-DR3/DR4 associations. IPEX: X-linked recessive, FOXP3 mutations.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
APS-1 is caused by AIRE gene mutations leading to impaired expression of tissue-specific self-antigens, allowing autoreactive T cells to escape central tolerance. APS-2 involves HLA-DR3/DR4 associations and T cell-mediated autoimmunity. IPEX is due to FOXP3 mutations causing regulatory T cell deficiency.
3.1 Molecular Basis¶
AIRE gene mutations in APS-1 disrupt thymic expression of self-antigens, leading to autoimmunity. HLA-DR3/DR4 associations in APS-2 drive T cell-mediated attacks on endocrine organs. FOXP3 mutations in IPEX impair regulatory T cell function.
4. CLINICAL FEATURES¶
APS-1 presents with mucocutaneous candidiasis, hypoparathyroidism, and Addison’s disease. APS-2 involves autoimmune endocrinopathies like T1D, Addison’s disease, and thyroiditis. IPEX presents with enteropathy, T1D, and skin disease in infancy.
Table 401-3 Clinical Features and Recommended Follow-Up for APS-1 and APS-2¶
| 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 |
| COMPONENT DISEASE | RECOMMENDED EVALUATION |
|---|---|
| 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 B12 levels | |
| Splenic atrophy: Blood smear for Howell-Jolly bodies; platelet count; ultrasound if positive | |
| Type 1 diabetes: Glucose, hemoglobin A1c, diabetes-associated 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 | |
| Serositis: Dictated by signs and symptoms of disease | |
| Stiff man syndrome: Dictated by signs and symptoms of disease | |
| Vitiligo: Physical examination, NALP-1 polymorphism |
4.1 Complications¶
APS-1: Chronic diarrhea, ectodermal dysplasia, dental enamel hypoplasia. APS-2: Celiac disease, myasthenia gravis, vitiligo. IPEX: Neurological deficits, progressive disability.
5. DIFFERENTIAL DIAGNOSIS¶
Differential diagnoses include isolated endocrinopathies, other autoimmune disorders (e.g., SLE, Sjögren’s), and genetic syndromes (e.g., Down’s syndrome, Turner’s syndrome).
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis relies on clinical criteria, autoantibody detection (e.g., anti-21-hydroxylase, anti-insulin, anti-TSH receptor), and genetic testing (AIRE for APS-1, HLA for APS-2).
6.1 Diagnostic Criteria¶
APS-1: Presence of two of three major disorders (Addison’s, hypoparathyroidism, mucocutaneous candidiasis). APS-2: Two or more endocrine deficiencies (Addison’s, T1D, thyroiditis).
7. MANAGEMENT & TREATMENT¶
Management includes hormone replacement (glucocorticoids, calcium, insulin), immunosuppression (rituximab, cyclophosphamide), and targeted therapies for individual component disorders. Hematopoietic stem cell transplantation is curative for IPEX.
7.1 Treatment Algorithms¶
- Hormone replacement for adrenal, thyroid, and parathyroid insufficiency. 2. Immunosuppressive therapy for autoimmune components. 3. Stem cell transplantation for IPEX. 4. Regular monitoring for associated autoimmune diseases.
8. PROGNOSIS & COMPLICATIONS¶
APS-1 has a variable prognosis with severe complications (e.g., adrenal crisis). APS-2 has a better prognosis but may lead to multiple autoimmune disorders. IPEX is often fatal in infancy without treatment.
8.1 Complications¶
APS-1: Adrenal crisis, malabsorption, ectodermal dysplasia. APS-2: Celiac disease, myasthenia gravis, hypophysitis. IPEX: Neurological deficits, progressive disability.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: Monitor for adrenal insufficiency and gestational diabetes. Pediatrics: Early screening for celiac disease and hypoparathyroidism. Elderly: Monitor for hypothyroidism and osteoporosis.
9.1 Genetic Counseling¶
APS-1: Autosomal recessive, family screening. APS-2: Polygenic, HLA risk assessment. IPEX: X-linked, carrier testing for female relatives.
10. KEY POINTS & CLINICAL PEARLS¶
- APS-1 is caused by AIRE mutations, APS-2 by HLA-DR3/DR4.
- Diagnose with clinical criteria and autoantibody testing.
- Treat with hormone replacement and immunosuppression.
- IPEX requires stem cell transplantation.
- Screen for associated autoimmune diseases regularly.