Coats's disease: definition and pathogenesis.

IT is remarkable that only one or two writers on Coats's disease appear to have been aware of the fact that Coats had written TWO articles on retinal disease with massive exudation: (1) his primary paper which appeared in the English language (1908), and (2) his final article which was published 4 years later (1912) in the German language. In the second paper, which has apparently been overlooked by most students of Coats's disease, the author gave evidence that his opinion had changed somewhat in the intervening years. In 1908 Coats divided his cases into two groups: those with and those without gross vascular disease and also mentioned "a very peculiar group, perhaps related to these two, which is characterized by the formation of large arteriovenous communications". In his final paper Coats placed his two former groups together because the similarities between the two groups were probably greater than the differences ("die Ahnlichkeiten sind wahrscheinlich gr6sser als die Unterschiede ... ich werde sie zusammengruppieren"), and he eliminated the third group because von Hippel had shown that this condition was in fact a retinal angiomatosis and, therefore, quite different from that described by Coats (".... der Zustand ist in Wahrheit eine Angiomatosis der Retina und daher verschieden von den hier berichteten Fallen. Aus diesen Grund unterlasse ich weitere Betrachtung dieser Gruppe").