It is hard to say how I ended up on a website for orphan diseases. A site http://www.orphadata.org allows to access a few files with orphan disease data (epidemiological, clinical and genetic) in XML format. XML data are easy to convert in a spreadsheet using MS Excel in Windows but LibreOffice on linux kept returning an error message. Another option would be to write an XSLT file to convert XML data into another format. Luckily, there is also a library in R for direct import from XML files.