Don't forget the zebra: Five rare diseases the emergency department team should be aware of

In Germany approximately 4 million people are affected by a rare disease (RD). Although individually they are rare (prevalence < 1:2000), taken together RDs are common, they occur more often than expected in the emergency department (ED), are repeatedly overlooked and pose a particular challenge to the ED team. This article presents five RDs as examples of diseases that an ED team should be aware of, recognize and be able to manage initially: acute porphyrias, thrombotic thrombocytopenic purpura, hereditary angioedema, hereditary hemorrhagic telangiectasia (Osler's disease) and urea cycle defects. At least one acute symptomatic or causal treatment option is available for each of these diseases but a previous diagnosis is essential. Using these examples, the article aims to raise awareness for RD in emergency medicine and proposes a diagnostic pathway in each case. This enables the ED team to initiate treatment early and can prevent unfavorable or even life-threatening disease progression.