Organ-specific and non-organ-specific autoantibodies in children and young adults with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED)

Abstract

OBJECTIVE: The aim of the study was to assess the complex of autoantibodies which can be detected in patients with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED), a rare autosomal recessive disease in which the extent of autoimmunity is still unknown. DESIGN: Antibodies (A) to parathyroid glands, adrenal cortex (AC-A), ovary and testis (steroid cell antibodies, SC-A), pancreatic islet cells (IC-A), gastric parietal cells, and non-organ-specific antigens were investigated in 11 APECED patients living in the Salento region of southern Italy. Further measurements included antibodies to cytochrome P450 (CYP) enzymes: cholesterol side-chain cleavage enzyme (CYP11A), 21-hydroxylase (CYP21) and 17alpha-hydroxylase (CYP17); and to glutamic acid decarboxylase 65-kDa isoform (GAD65), tyrosine phosphatase-like protein IA2, thyroglobulin (TG), thyroperoxidase (TPO), thyrotropin receptor, liver CYP enzymes and intrinsic factor. METHODS: Antibodies to organs and subcellular fractions were detected by immunofluorescence. Radiobinding, immunoradiometric, and immunoblotting assays were used for the other measurements. RESULTS: AC-A and SC-A were positive in all sera; among antibodies to adrenal CYP enzymes, only CYP21-A were present in all the patients with Addison's disease of short-medium duration (<15 years). Of three patients with Addison's disease of long duration (>15 years), two tested positive for antibodies to all three CYP enzymes, and the other for only CYP11A-A. In all sera CYP11A-A and/or CYP17-A were found. Two patients tested positive for both IC-A and GAD65-A, one for both IC-A and IA2-A, and one for GAD65-A; the fasting C-peptide assay showed no statistical difference between these four subjects and the others. All four hypothyroid patients were positive for TPO-A, while two of them were positive and two were negative for TG-A; two euthyroid subjects had positivity for TG-A. Liver-kidney microsomal antibodies reacting against the CYP2A6 were detected in two patients with autoimmune hepatitis. All but one sera contained anti-nuclear antibodies at a titre ranging between 1:20 and 1:80; however, only two patients had a connective tissue disease (Sjogren's syndrome). CONCLUSIONS: Several autoantibodies may be detected in any APECED patient. Our data confirm that CYP21-A and TPO-A are major autoantibodies involved in APECED-associated Addison's disease and hypothyroidism respectively, while CYP11A-A and CYP17-A correlate with positivity for SC-A. Markers of islet cell autoimmunity are frequent, but prevalence and modalities of progression to overt beta-cell failure have to be clarified. Low-titre non-organ-specific autoantibodies are a feature of autoimmunity in APECED, but their role has yet to be fully explained.