The Delphi process is illustrated.

<p>In the Delphi survey, a total of 474 experts were contacted initially. During the second round, 95 participated. All participants were invited to answer two questions.</p

Categories of shared phenomena in individuals with a rare disease.

<p>Categories of shared phenomena in individuals with a rare disease.</p

Rare diseases with need for diagnostic support (2nd Delphi round).

<p>Rare diseases with need for diagnostic support (2nd Delphi round).</p

Background of participants responding to the first Delphi inquiry.

<p>Background of participants responding to the first Delphi inquiry.</p

First 20 diseases with utmost need for diagnostic support identified in the first Delphi round^*.

<p>First 20 diseases with utmost need for diagnostic support identified in the first Delphi round^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172532#t002fn001" target="_blank">*</a>}.</p