Changes in clinical practice with the unravelling of diseases: connective-tissue disorders.

Unravelling of diseases is achieved in steps by sequentially describing their phenotype, natural course, aetiology and pathogenesis. Through succinct clinical observation, conglomerates of heterogeneous connective-tissue disorders, such as various forms of disproportionate dwarfism, have been split into well-defined entities. They have often been confirmed by biochemical and molecular analysis. On the other hand, seemingly disparate disorders have been shown to be pathogenetically related and to be variable expressions of common defects. Examples are the mucopolysaccharidoses and type II collagenopathies. Disease recognition through splitting and lumping has improved prevention and prognostication. It is the basic requirement for future therapeutic attempts on a pathogenetic or molecular level.