Jaakko Perheentupa

Clinical Variation of Autoimmune Polyendocrinopathy–Candidiasis–Ectodermal Dystrophy (APECED) in a Series of 68 Patients

To define the clinical picture and course of the autosomal recessive disease called autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED), we report data from our 10-month to 31-year follow-up of 68 patients from 54 families, now 10 months to 53 years of age. The clinical manifestations varied greatly and included from one to eight disease components, 63 percent of the patients having three to five of them. The initial manifestation was oral candidiasis in 41 patients (60 percent), intestinal malabsorption in 6 (9 percent), and keratopathy in 2 (3 percent). All the patients had candidiasis at some time. The earliest endocrine component appeared at 19 months to 35 years of age. Hypoparathyroidism was present in 54 patients (79 percent), adrenocortical failure in 49 (72 percent), and gonadal failure in 15 (60 percent) of the female patients greater than or equal to 13 years of age and 4 (14 percent) of the male patients greater than or equal to 16 years of age. There were multiple endocrine deficiencies in half the patients. From 4 to 29 percent of the patients had periodic malabsorption, gastric parietal-cell atrophy, hepatitis, alopecia, vitiligo, or a combination of these conditions. Dental-enamel hypoplasia and keratopathy were also frequent but were not attributable to hypoparathyroidism. In the patients whose initial manifestation (other than candidiasis) was adrenal failure, the other components developed less often than in the remaining patients. We conclude that the clinical spectrum in patients with APECED is broad. The majority of patients have three to five manifestations, some of which may not appear until the fifth decade. Therefore, all patients need lifelong follow-up for the detection of new components of the disease.

Chronic mucocutaneous candidiasis in APECED or thymoma patients correlates with autoimmunity to Th17-associated cytokines

Chronic mucocutaneous candidiasis (CMC) is frequently associated with T cell immunodeficiencies. Specifically, the proinflammatory IL-17A–producing Th17 subset is implicated in protection against fungi at epithelial surfaces. In autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED, or autoimmune polyendocrine syndrome 1), CMC is often the first sign, but the underlying immunodeficiency is a long-standing puzzle. In contrast, the subsequent endocrine features are clearly autoimmune, resulting from defects in thymic self-tolerance induction caused by mutations in the autoimmune regulator (AIRE). We report severely reduced IL-17F and IL-22 responses to both Candida albicans antigens and polyclonal stimulation in APECED patients with CMC. Surprisingly, these reductions are strongly associated with neutralizing autoantibodies to IL-17F and IL-22, whereas responses were normal and autoantibodies infrequent in APECED patients without CMC. Our multicenter survey revealed neutralizing autoantibodies against IL-17A (41%), IL-17F (75%), and/ or IL-22 (91%) in >150 APECED patients, especially those with CMC. We independently found autoantibodies against these Th17-produced cytokines in rare thymoma patients with CMC. The autoantibodies preceded the CMC in all informative cases. We conclude that IL-22 and IL-17F are key natural defenders against CMC and that the immunodeficiency underlying CMC in both patient groups has an autoimmune basis.

Mutations in the AIRE Gene: Effects on Subcellular Location and Transactivation Function of the Autoimmune Polyendocrinopathy-Candidiasis–Ectodermal Dystrophy Protein

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a monogenic autosomal disease with recessive inheritance. It is characterized by multiple autoimmune endocrinopathies, chronic mucocutaneous candidiasis, and ectodermal dystrophies. The defective gene responsible for this disease was recently isolated, and several different mutations in the novel gene, AIRE, have been identified, by us and by others, in patients with APECED. We have shown that the APECED protein is mainly localized, both in vitro and in vivo, to the cell nucleus, where it forms distinct speckles. This accords with the predicted structural features of the protein, which suggest involvement of AIRE in the regulation of gene transcription. Here, we report the results of mutational analyses of a series of 112 patients with APECED who were from various ethnic backgrounds. A total of 16 different mutations, covering 91% of disease alleles, were observed; of these, 8 were novel. The mutations are spread throughout the coding region of AIRE, yet four evident mutational hotspots were observed. In vitro expression of four different naturally occurring nonsense and missense mutations revealed a dramatically altered subcellular location of the protein in cultured cells. Interestingly, the wild-type APECED protein tethered to the Gal4 DNA-binding domain acted as a strong transcriptional activator of reporter genes in mammalian cells, whereas most of the analyzed mutant polypeptides had lost this capacity.

Anti-Interferon Autoantibodies in Autoimmune Polyendocrinopathy Syndrome Type 1

Background The autoimmune regulator (AIRE) gene influences thymic self-tolerance induction. In autoimmune polyendocrinopathy syndrome type 1 (APS1; OMIM 240300), recessive AIRE mutations lead to autoimmunity targetting endocrine and other epithelial tissues, although chronic candidiasis usually appears first. Autoimmunity and chronic candidiasis can associate with thymomas as well. Patients with these tumours frequently also have high titre immunoglobulin G autoantibodies neutralising type I interferon (IFN)–α and IFN-ω, which are secreted signalling proteins of the cytokine superfamily involved in both innate and adaptive immunity. Methods and Findings We tested for serum autoantibodies to type I IFNs and other immunoregulatory cytokines using specific binding and neutralisation assays. Unexpectedly, in 60/60 Finnish and 16/16 Norwegian APS1 patients with both AIRE alleles mutated, we found high titre neutralising immunoglobulin G autoantibodies to most IFN-α subtypes and especially IFN-ω (60% homologous to IFN-α)—mostly in the earliest samples. We found lower titres against IFN-β (30% homologous to IFN-α) in 23% of patients; two-thirds of these (from Finland only) also had low titres against the distantly related “type III IFN” (IFN-λ1; alias interleukin-29). However, autoantibodies to the unrelated type II IFN, IFN-γ, and other immunoregulatory cytokines, such as interleukin-10 and interleukin-12, were much rarer and did not neutralise. Neutralising titres against type I IFNs averaged even higher in patients with APS1 than in patients with thymomas. Anti–type I IFN autoantibodies preceded overt candidiasis (and several of the autoimmune disorders) in the informative patients, and persisted for decades thereafter. They were undetectable in unaffected heterozygous relatives of APS1 probands (except for low titres against IFN-λ1), in APS2 patients, and in isolated cases of the endocrine diseases most typical of APS1, so they appear to be APS1-specific. Looking for potentially autoimmunising cell types, we found numerous IFN-α+ antigen-presenting cells—plus strong evidence of local IFN secretion—in the normal thymic medulla (where AIRE expression is strongest), and also in normal germinal centres, where it could perpetuate these autoantibody responses once initiated. IFN-α2 and IFN-α8 transcripts were also more abundant in antigen-presenting cells cultured from an APS1 patients blood than from age-matched healthy controls. Conclusions These apparently spontaneous autoantibody responses to IFNs, particularly IFN-α and IFN-ω, segregate like a recessive trait; their high “penetrance” is especially remarkable for such a variable condition. Their apparent restriction to APS1 patients implies practical value in the clinic, e.g., in diagnosing unusual or prodromal AIRE-mutant patients with only single components of APS1, and possibly in prognosis if they prove to predict its onset. These autoantibody responses also raise numerous questions, e.g., about the rarity of other infections in APS1. Moreover, there must also be clues to autoimmunising mechanisms/cell types in the hierarchy of preferences for IFN-ω, IFN-α8, IFN-α2, and IFN-β and IFN-λ1.

Congenital Chloride Diarrhea

Specific disturbances of intestinal electrolyte transport are very rare. More often, absorption of water and electrolytes is impaired along with the absorption of amino acids, fatty acids, sugars, and vitamins in states of generalized malabsorption, as in familial enteropathy with hypoplastic villous atrophy (Davidson et al. 1978). Chronic inflammation of the gut, e.g., colitis ulcerosa, may also be accompanied by malabsorption of electrolytes and water (Dutchie et al. 1964; Edmonds and Pilcher 1973; Harris and Shield 1970; Rask-Madsen 1973). In addition, reversible electrolyte malabsorption, “secondary chloride-losing diarrhea” may result from intestinal surgery even in normal children (Aaronson 1971). Other factors causing secondary impairment may be increased levels of gastrointestinal hormones, VIP, GIP, gastrin, secretin (Walsh 1981), and calcitonin (Gray et al. 1973) produced by tumors, diseases with increased intestinal bile acid concentrations (Binder 1980), and infections with intestinal toxin production such as cholera and E. coli gastroenteritis (Fishman 1980; Sack 1975). The only ions known to be involved in specific malabsorption states are Zn+ (Rahanzadeh and Danzig 1974), Cu2+ (Danks et al. 1972) and C1-. Malabsorption of C1- is known as congenital chloride diarrhea (CCD). This disease was at first namend “congenital alkalosis with diarrhea” (Darrow 1945; Gamble et al. 1945). Later, it was called “congenital chloridorrhea” and “familial chloride diarrhea.” Today the name “congenital chloride diarrhea” appears to be generally accepted.

Clinical manifestations and management of patients with autoimmune polyendocrine syndrome type I

Autoimmune polyendocrine syndrome type I (APS‐I) is a monogenic model disease of autoimmunity. Its hallmarks are chronic mucocutaneous candidosis, hypoparathyroidism and adrenal insufficiency, but many other autoimmune disease components occur less frequently. The first components usually appear in childhood, but may be delayed to adolescence or early adult life. There is enormous variation in presentation and phenotype, which makes the diagnosis difficult. Antibodies against interferon‐ω and ‐α have recently been shown to be sensitive and relatively specific markers for APS‐I, and mutational analysis of the autoimmune regulator gene gives the diagnosis in >95% of cases. The treatment and follow‐up of patients is demanding and requires the collaboration of specialists of several fields. However, the literature is especially sparse regarding information on treatment and follow‐up; hence, we present here a comprehensive overview on clinical characteristics, treatment and follow‐up based on personal experience and published studies.

Autoimmune Polyendocrine Syndrome Type 1 and NALP5, a Parathyroid Autoantigen

BACKGROUND Autoimmune polyendocrine syndrome type 1 (APS-1) is a multiorgan autoimmune disorder caused by mutations in AIRE, the autoimmune regulator gene. Though recent studies concerning AIRE deficiency have begun to elucidate the molecular pathogenesis of organ-specific autoimmunity in patients with APS-1, the autoantigen responsible for hypoparathyroidism, a hallmark of APS-1 and its most common autoimmune endocrinopathy, has not yet been identified. METHODS We performed immunoscreening of a human parathyroid complementary DNA library, using serum samples from patients with APS-1 and hypoparathyroidism, to identify patients with reactivity to the NACHT leucine-rich-repeat protein 5 (NALP5). Subsequently, serum samples from 87 patients with APS-1 and 293 controls, including patients with other autoimmune disorders, were used to determine the frequency and specificity of autoantibodies against NALP5. In addition, the expression of NALP5 was investigated in various tissues. RESULTS NALP5-specific autoantibodies were detected in 49% of the patients with APS-1 and hypoparathyroidism but were absent in all patients with APS-1 but without hypoparathyroidism, in all patients with other autoimmune endocrine disorders, and in all healthy controls. NALP5 was predominantly expressed in the cytoplasm of parathyroid chief cells. CONCLUSIONS NALP5 appears to be a tissue-specific autoantigen involved in hypoparathyroidism in patients with APS-1. Autoantibodies against NALP5 appear to be highly specific and may be diagnostic for this prominent component of APS-1.

APS-I/APECED: the clinical disease and therapy

The clinical picture and course of APS-I or APD-I/APECED is widely variable: the list of possible disease components includes some 30 disorders. The initial manifestation may not include any of the known characteristic components, namely, mucocutaneous candidiasis, hypoparathyroidism, or adrenocortical insufficiency. Although mutation detection is available, it does not help to exclude this disease. Diagnostic strategy needs to be based on knowledge of the clinical picture, including the features of ectodermal dystrophy.

A Defect of Regulatory T Cells in Patients with Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED), a monogenic recessive disease characterized by autoimmunity against multiple tissues, offers a unique possibility to study the breakdown of self-tolerance in humans. It is caused by mutations in the autoimmune regulator gene (AIRE), which encodes a transcriptional regulator. Work using Aire−/− mice suggests that Aire induces ectopic expression of peripheral Ags and promotes their presentation in the thymus. We have explored reasons for the difference between the comparatively mild phenotype of Aire-deficient mice and human APECED patients. We provide evidence that, unlike in the Aire−/− mice, in the patients a key mediator of active tolerance, the CD4+CD25+ regulatory T (Treg) cell subset is impaired. This was shown by significantly decreased expression of FOXP3 mRNA and protein, decreased function, and alterations in TCR repertoire. Also, in the normal human thymus a concentric accumulation of AIRE+ cells was seen around thymic Hassall’s corpuscles, suggesting that in the patients these cells may be involved in the observed Treg cell failure. In Aire−/− mice the expression of FoxP3 was normal and even increased in target tissues in parallel with the lymphocyte infiltration process. Our results suggest that a Treg cell defect is involved in the pathogenesis of APECED and emphasize the importance of active tolerance mechanisms in preventing human autoimmunity.

Identification of tryptophan hydroxylase as an intestinal autoantigen.

BACKGROUND Autoimmune polyendocrine syndrome type 1 (APS1) is an autosomal recessive disorder with both endocrine and non-endocrine features. Periodic gastrointestinal dysfunction occurs in 25-30% of APS1 patients. We aimed to identify an intestinal autoantigen. METHODS A human duodenal cDNA library was immunoscreened with serum samples from APS1 patients. A positive clone was identified and used for in-vitro transcription and translation, followed by immunoprecipitation with serum samples from 80 APS1 patients from Norway, Finland, and Sweden. Sections of normal and APS1-affected small intestine were immunostained with serum from APS1 patients and specific antibodies. An enzyme-inhibition assay was used to characterise the autoantibodies. FINDINGS We isolated a cDNA clone coding for tryptophan hydroxylase. 48% (38/80) of APS1 patients had antibodies to tryptophan hydroxylase, whereas no reactivity to this antigen was detected in patients with other autoimmune diseases (n=372) or healthy blood donors (n=70). 89% (17/19) of APS1 patients with gastrointestinal dysfunction were positive for antibodies to tryptophan hydroxylase, compared with 34% (21/61) of patients with no gastrointestinal dysfunction (p<0.0001). Serum from antibody-positive APS1 patients specifically immunostained tryptophan-hydroxylase-containing enterochromaffin cells in normal duodenal mucosa. No serotonin-containing cells were seen in duodenal biopsy samples from APS1 patients. Serum from antibody-positive APS1 patients almost completely inhibited activity of tryptophan hydroxylase. INTERPRETATION Tryptophan hydroxylase is an endogenous intestinal autoantigen in APS1, and there is an association between antibodies to the antigen and gastrointestinal dysfunction. Analysis of antibodies to tryptophan hydroxylase may be a valuable diagnostic tool to predict and monitor gastrointestinal dysfunction in APS1.