Barrabas suggested the existence of three forms of the disorder, and Beighton later recognized two more forms. To date, there are 11 types described, each with distinctive features, although phenotypic overlap is present. Type I, or Gravis variety, is the classic, severe disorder characterized by marked skin hyperextensibility and joint hypermobility. The skin is typically soft and velvety in texture with increased compliance. Easy bruisability is common and trauma results in gaping, fish-mouth type wounds which bleed less than expected.
Prematurity is common, presumably because of fragility of the fetal membranes.
Type I is inherited in an autosomal dominant manner with complete penetrance. New mutations are common. No distinctive biochemical tests are available, but the diagnosis generally is not ambiguous. The clinical features of type II, the Mitis form, are similar to those of EDS Type I, but milder. It, too, is inherited in an autosomal dominant fashion.