An 8-year-old boy presented in 1995 with a 2-year history of hypertransaminasemia and hypergammaglobulinemia. Afterwards the patient displayed onychosis with a positive culture test for Candida albicans (CA). Because of the persistence of hypertransaminasemia, a percutaneous liver biopsy was performed showing 'low grade chronic active autoimmune hepatitis' (AIH), positive for liver-kidney microsomal autoantibodies and antibodies to the hepatic autoantigen cytochrome P450-1A2. Immunosuppressive treatment was initiated. In 2003 he developed Addison's disease resulting in the diagnosis of autoimmune polyendocrinopathy candidiasis-ectodermal dysplasia (APECED) syndrome, also known as autoimmune polyendocrine syndrome type 1 (APS1). Anti-17OH hydroxylase antibodies tested negative, anti-21-OH hydroxylase autoantibodies were positive. Among the other relevant organ- and non organ- specific autoantibodies, aromatic L-amino acid decarboxylase (ADDC) autoantibodies and anti-tryptophan hydroxylase autoantibodies were positive. The patient also presented polyuria and polydypsia with diabetes insipidus. Because of the presence of two diagnostic criteria of APS1, mutations in the autoimmune regulator gene (AIRE) were performed, which revealed the presence of a novel mutation (c1314- 1326 del 13/insGT) in exon 11. In conclusion, the diagnosis of APECED should be suspected in any child with minimal hypertransaminasemia, anti-microsomal autoantibodies and Candida albicans onychosis.