How rare is rare? A literature survey of the last 45 years of paleopathological research on ancient rare diseases.

OBJECTIVE: This paper aims to provide a quantitative estimation of the representation of diseases defined as rare today in the bioarchaeological literature and to outline the reasons for this. MATERIALS: A 45-year bibliometric study of publications in seven bioarchaeological journals, along with two journals and editorial groups of broader scientific focus. METHODS: Analyses of distribution patterns of the search hits and diachronic trends for achondroplasia, autosomal-dominant osteopetrosis, osteogenesis imperfecta, and osteopoikilosis, compared to those for tuberculosis as control measure of coverage. RESULTS: Studies of ancient rare diseases (ARD) are mostly published as case reports in specialized journals and their number did not benefit from the introduction of biomolecular studies. The higher frequency of cases of achondroplasia suggests that not all rare diseases are equally under-represented. CONCLUSIONS: Rare diseases are still largely under-represented in bioarchaeological literature. Their marginality likely results from a combination of taphonomic, methodological and public visibility factors. SIGNIFICANCE: This article is the first attempt to provide a quantitative assessment of the under-representation of ARD and to outline the factors behind it. LIMITATIONS: Rare diseases are an etiologically heterogeneous group. The number of surveyed journals and articles, as well as targeted diseases might be limiting factors. SUGGESTIONS FOR FURTHER RESEARCH: Increasing collection and dissemination of data on ARD; opening a wide-ranging debate on their definition; implementation of biomolecular studies.