Objective: To investigate the phenotype and genotype of 3 unrelated children with triple A syndrome from southern Turkey. Methods: The coding sequence of the AAAS gene was sequenced including exon-intron boundaries. Haplotype analysis using markers from AAAS region was performed in order to assess potential founder effects. Results: In all 3 patients, the identical nonsense mutation (R478X) in exon 16 of the AAAS gene was identified. The patients who may be distantly related appeared phenotypically similar with the classical triad of the triple A syndrome (adrenal insufficiency, alacrima and achalasia) with dermatological manifestations while lacking neurological features except for mild mental retardation. Conclusion: The R478X mutation tends to result in a rather severe phenotype although genotype-phenotype relationships cannot be drawn due to the small number of patients. Copyright (C) 2004 S. Karger AG, Basel.