In the past few years, interest in rare diseases has grown, as demonstrated by the agendas of politicians and health authorities, but too little attention is still paid to ultra-rare diseases. Although no legal definition of an “ultra-rare” disease has yet been established, this subcategory was informally introduced by the National Institute for Health and Care Excellence for drugs with indications for diseases that have a prevalence <1 per 50 000 persons 1–3. Too little attention is still paid to ultra-rare diseases. It is important to disseminate the best information on less common diseases in order to improve the clinical managment and improve care. https://bit.ly/2NougE5