BACKGROUND: Pseudoxanthoma elasticum (PXE) is a genetic disorder due to mutations in the gene encoding the transmembrane transporter protein adenosine triphosphate binding cassette (ABC)-C6, resulting in calcification of elastic fibres in the skin, eyes and cardiovascular system. OBJECTIVES: To evaluate the diagnostic criteria for PXE based on molecular data. METHODS: Of 10 families with a positive history of PXE 142 subjects were investigated for clinical symptoms, histological findings and genetic haplotype analysis. RESULTS: Of these, 25 subjects were haplotypic homozygous for PXE and 23 had typical clinical and histopathological manifestations. Two of the 25 patients showed such marked solar elastosis and macular degeneration that PXE could not be confirmed clinically. Sixty-seven subjects were haplotypic heterozygous carriers and 50 were haplotypic homozygous unaffected. Of these 117 subjects, 116 showed no cutaneous or ophthalmological signs of PXE. In one of the 50 haplotypic homozygous unaffected patients important solar elastosis and scarring of the retina mimicked PXE lesions. Only four of the 67 haplotypic heterozygous carriers had biopsies of nonlesional skin; all were histopathologically normal. CONCLUSIONS: In our patients, PXE presents as an autosomal recessive genodermatosis. Correlation of haplotype and phenotype confirmed actual major diagnostic criteria. In patients with marked solar elastosis and/or severe macular degeneration clinical diagnosis can be impossible and molecular testing is needed to confirm the presence of PXE. To the best of our knowledge our large study compares for the first time clinical findings with molecular data.