The epidemiology of rare diseases

“Who am I – and if so, how many?”

Fri, 2021 / 03 / 12
Rare diseases not only pose a great challenge to the development of novel therapies, but also generate difficulties for treating physicians to make a diagnosis and for patients to classify their own situation – true to the famous question raised by philosopher and publicist Richard David Precht "Who am I – and if so, how many?".

Precht aims to discuss fundamental philosophical questions about human consciousness and behaviour. But especially in relation to people suffering from a rare (< 50 cases per 100,000 persons) or even ultra-rare disease (< 2 cases per 100,000 persons), this citation shows one of the key points of the burden on patients created by such diseases.

The low epidemiological numbers are usually accompanied by low disease awareness of a rare diseases. This, especially in connection with the occurrence of unspecific symptoms and heterogeneous progression, makes it much more difficult for doctors to make a diagnosis. In some cases, a reliable diagnosis and treatment of rare diseases is only possible in specialised centres. Therefore, patients with rare diseases in particular often experience a diagnostic journey that may last for several years until the "right" diagnosis is finally made, and they can assign themselves as patients to a specific disease. Following this, patients are often left with the question: "Am I alone with this disease?" The search for like-minded people who are suffering in a similar way begins. Specific help is available to sufferers through patient organisations, among others, which make it much easier to get in touch with people with the same condition.

When considering those typical problems of rare diseases, it is important to obtain a reliable assessment of their epidemiology. One methodological approach for the determination of prevalence and incidence is the study of claims data, which are data based on the billing and reimbursement of services provided by statutory health insurances (click here for information on claims data analyses). Recently, a study of the epidemiology of patients with ANCA-associated vasculitis (AAV) (click here to view the publication), a group of potentially life-threatening, rare autoimmune diseases, was published under the co-authorship of SKC. Based on claims data, this study concludes that AAV may be almost twice as frequent in Germany as suspected from previous surveys. Such a gain in information can influence the allocation of resources in the health care system and thus may improve the care situation of patients. Last but not least, it also represents important information for the AAV patients themselves and their community.


  • „Wer bin ich - und wenn ja wie viele?: Eine philosophische Reise", Richard David Precht, Goldmann Verlag (2007)
  • Hellmich et al. 2021 „New insights into the epidemiology of ANCA-associated vasculitides in Germany: results from a claims data study", DOI: 10.1093/rheumatology/keaa924
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