The role of case studies in recent paleopathological literature: An argument for continuing relevance

The Digital Atlas of Ancient Rare Diseases (DAARD) and its relevance for current research

BACKGROUND

The history of rare diseases is largely unknown. Research on this topic has focused on individual cases of prominent (historical) individuals and artistic (e.g., iconographic) representations. Medical collections include large numbers of specimens that exhibit signs of rare diseases, but most of them date to relatively recent periods. However, cases of rare diseases detected in mummies and skeletal remains derived from archaeological excavations have also been recorded. Nevertheless, this direct evidence from historical and archaeological contexts is mainly absent from academic discourse and generally not consulted in medical research on rare diseases.

RESULTS

This desideratum is addressed by the Digital Atlas of Ancient Rare Diseases (DAARD: https://daard.dainst.org ), which is an open access/open data database and web-based mapping tool that collects evidence of different rare diseases found in skeletons and mummies globally and throughout all historic and prehistoric time periods. This easily searchable database allows queries by diagnosis, the preservation level of human remains, research methodology, place of curation and publications. In this manuscript, the design and functionality of the DAARD are illustrated using examples of achondroplasia and other types of stunted growth.

CONCLUSIONS

As an open, collaborative repository for collecting, mapping and querying well-structured medical data on individuals from ancient times, the DAARD opens new avenues of research. Over time, the number of rare diseases will increase through the addition of new cases from varied backgrounds such as museum collections and archaeological excavations. Depending on the research question, phenotypic or genetic information can be retrieved, as well as information on the general occurrence of a rare disease in selected space-time intervals. Furthermore, for individuals diagnosed with a rare disease, this approach can help them to build identity and reveal an aspect of their condition they might not have been aware of. Thus, the DAARD contributes to the understanding of rare diseases from a long-term perspective and adds to the latest medical research.

The role of dietary calcium in the etiology of childhood rickets in the past and the present

For more than two centuries, lack of sunlight has been understood to cause vitamin D deficiency and documented as a primary cause of rickets. As such, evidence of rickets in the archeological record has been used as a proxy for vitamin D status in past individuals and populations. In the last decade, a clinical global consensus has emerged wherein it is recognized that dietary calcium deficiency also plays a role in the manifestation of rickets and classic skeletal deformities may not form if dietary calcium is normal even if vitamin D is deficient. This disease is now clinically called "nutritional rickets" to reflect the fact that rickets can take calcium deficiency-predominant or vitamin D deficiency-predominant forms. However, there are currently no paleopathological studies wherein dietary calcium deficiency is critically considered a primary etiology of the disease. We review here the interplay of calcium, vitamin D, and phosphorous in bone homeostasis, examine the role of dietary calcium in human health, and critically explore the clinical literature on calcium deficiency-predominant rickets. Finally, we report a case of rickets from the late Formative Period (~2500-1500 years ago) of the Atacama Desert and argue the disease in this infant is likely an example of calcium deficiency-predominant rickets. We conclude that most archeological cases of rickets are the result of multiple micronutrient deficiencies that compound to manifest in macroscopic skeletal lesions. For clinicians, these factors are important for implementing best treatment practice, and for paleopathologists they are necessary for appropriate interpretation of health in past communities.