Lessons From Prospective Longitudinal Follow-up of a French APECED Cohort

Abstract

Background: Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome is a rare disease caused by biallelic mutations of the AIRE gene, usually presenting with the triad hypoparathyroidism-adrenal failure-chronic mucocutaneous candidiasis (CMC) and nonendocrine manifestations. The aim of this study was to determine the molecular profile of the AIRE gene, the prevalence of rare manifestations, and to characterize immunological disturbances in a French cohort.

Patients and methods: A national, multicenter prospective observational study to collect genetic, clinical, biological, and immunological data (NCT03751683).

Results: Twenty-five patients (23 families) were enrolled. Eleven distinct AIRE variants were identified, 2 of which were not previously reported: an intronic variant, c.653-70G > A, and a c.1066del (p.Arg356GlyfsX22) variant (exon 9). The most common was the Finnish variant c.769C > T (16 alleles), followed by the variant c.967_979del13 (15 alleles), which seemed associated with a less severe phenotype. Seventeen out of 25 patients were homozygote. The median number of clinical manifestations was 7; 19/25 patients presented with the hypoparathyroidism-adrenal failure-CMC triad, 8/13 showed pulmonary involvement, 20/25 had ectodermal dystrophy, 8/25 had malabsorption, and 6/23 had asplenia. Fifteen out of 19 patients had natural killer cell lymphopenia with an increase in CD4+ and CD8+ T lymphocytes and an age-dependent alteration of B lymphocyte homeostasis compared with matched controls (P < .001), related to the severity of the disease. All tested sera (n = 18) were positive for anti-interferon-α, 15/18 for anti-IL-22 antibodies, and 13/18 for anti-IL-17F antibodies, without clear phenotypic correlation other than with CMC.

Conclusion: This first prospective cohort showed a high AIRE genotype variability, with 2 new gene variants. The prevalence of potentially life-threatening nonendocrine manifestations was higher with systematic screening. These manifestations could, along with age-dependent B-cell lymphopenia, contribute to disease severity. Systematic screening for all the manifestations of the syndrome would allow earlier diagnosis, supporting vaccination and targeted therapeutic approaches.

Keywords: AIRE genotype; APECED syndrome; asplenia; autoimmune polyendocrine syndrome type 1; pulmonary involvement.

Figure 1.

Study flow chart.

Figure 2.

Effect on splicing of the c.653-70G > A variant located in intron 5 of the AIRE gene, assessed using a functional minigene assay. (A) Schematic representation of the pCAS2-AIRE minigenes used in the splicing reporter assay. Boxes indicate exons, whereas lines in between represent introns. The minigenes were generated by inserting a genomic fragment, containing exon 6 of the AIRE exon (gray box), as well as part of the upstream and downstream flanking intronic sequences (thick lines), into the intron of the minigene using the BamHI and MluI restriction sites. Expression of the minigenes is driven by the human cytomegalovirus promoter. Arrows above the minigene exons A and B (white boxes) indicate the positions of primers used in RT-PCR analysis. (B) Analysis of the splicing pattern of the Wt and mutant pCAS2-AIRE minigenes for the c.653-70G > A and c.769C > T variants. Wt and mutant pCAS-AIRE constructs were transiently expressed in HeLa cells by transfection. The splicing patterns of the minigene transcripts were then analyzed by RT-PCR as previously described (24).The image shows the electrophoresis on a 2% agarose ethidium bromide-stained gel of the RT-PCR products obtained for each minigene. The identities of the RT-PCR products are indicated on the right. The c.653-70G > A variant allows the retention of 68 bp of intron 5 in the final transcript and a frameshift as the c.769C > T variant, as expected, has no splice effect. Abbreviation: Wt, wild-type.

Figure 3.

Patient #25 chest computed tomography scan and lung function tests. Bronchiectasis, honeycombing, micro and macrocystic parenchymal destruction, and ground-glass opacities. Abbreviations: FVC, forced vital capacity, FEV, forced expiratory volume in 1 second.