The preferred description for the Grönblad-Strandberg syndrome, pseudoxanthoma elasticum (PXE), refers only to the cutaneous aspect of the disease, although the skin is the least severely involved organ. The potential catastrophic manifestation of this heterogeneous heritable disorder is described in a dominant pedigree where mother and grandmother died because of major vascular problems. The family requested predictive testing of the three children. Diagnosis of PXE is usually performed by morphological examination of skin lesions, which reveal incrustations formed by inorganic ions (mainly calcium) and various organic (degraded?) materials in the elastin moiety of the elastic fibers. The ubiquitous elastic fibers in other organs and arteries may be similarly involved. Moreover, there is co-involvement of collagen fibrils at the electron microscopical level. The three adolescent siblings did not show any clinical PXE symptoms. However, ultrastructural investigation of overtly normal skin in predilection sites gave a positive diagnosis for this dominant PXE type. Dermal connective tissue showed a specific aberrant pattern: elastin of elastic fibers regularly contained small foci of calcification resembling those in perilesional skin of the mother and other PXE patients; in collagen bundles adjacent to altered elastic fibers, collagen fibrils occurred with thickened diameters and flower-like contours; ground substance material was increased. The possible pathogenetic mechanism and problems posed by predictive testing of adult-onset diseases are discussed.