From http://www.orpha.net/orphacom/cahiers/docs/GB/Prevalence_of_rare_diseases_by_decreasing_prevalence_or_cases.pdf which lists 1827 conditions. Reading the terms of use at http://www.orpha.net/consor/cgi-bin/Education_AboutOrphanet.php?lng=EN&stapage=CGU I suspect permission would need be sought to publish the entire list with its list of prevelances or cases/family numbers across Europe.

I wonder how many of these we have articles for. I note some terms might exist albeit rephrased, eg [Parkinson’s disease dementia, familial] might possibly be included in Parkinson’s disease or [Squamous cell carcinoma of head and neck] is clearly the article Squamous cell carcinoma.