Differential diagnosis of a diffuse sclerosis in an identified male skull (early 20th century Coimbra, Portugal): A multimethodological approach for the identification of osteosclerotic dysplasias in skeletonized individuals.

Objective: This work aims to discuss the difficulties in diagnosing osteosclerotic changes in skeletonized individuals and to raise awareness of osteosclerotic dysplasias as a group of rare ancient diseases.

Materials: The skull of a 62-year-old male individual from the International Exchange Skull Collection, curated by the University of Coimbra, who died in 1928 presenting albuminous nephritis (Bright disease)/uraemia as the registered cause of death.

Methods: The skull was macroscopically and radiologically examined and bone elemental analysis was investigated. The genealogy and medical records of the individual were also searched.

Results: The lesions are in accordance with an osteosclerotic process possibly pointing to osteosclerosis, osteosclerotic metaphyseal dysplasia, or dysosteosclerosis, but osteoclasia with hyperphosphatasia, endosteal hyperostosis, sclerosteosis, or osteopathia striata with cranial sclerosis cannot be ruled out.

Conclusions: Representativeness of the skeleton is a crucial feature in diagnosing rare diseases and, to avoid a misdiagnosis, the final diagnosis should include a group of diseases rather than a definite disease.

Significance: Difficulties in diagnosing rare diseases are discussed and best approaches in the study osteosclerotic dysplasias in skeletonized individuals are offered in the light of current clinical knowledge.

Limitations: The absence of the postcranial skeleton and of pathognomonic lesions associated with osteosclerotic dysplasias limits diagnosis. Although rare diseases often have a genetic basis, specific genetic testing for the diagnosis of rare diseases in paleopathological cases are not yet available.

Suggestions For Further Research: Future genetic studies might help narrow down the diagnosis.