To outline the importance of accurate diagnosis in ancient rare diseases by presenting a possible case of Langerhans-cell histiocytosis.
Skeletal elements from a well-preserved skeleton of a nine to eleven-year-old, probably female child who lived around 300-400 AD Late Roman Neuburg / Donau (Germany).
Macroscopic, radiologic, light and scanning-electron microscopic and physical techniques were used.
Resorptive defects, particularly in the cranium, but also in the left hip bone and the right femur, suggest the presence of Langerhans-cell histiocytosis macroscopically and radiologically. The presence of morphological changes along the edges of osteolytic lesions and in the diploic spaces appear to be post-mortem artifacts based on microscopic investigation and elemental analysis.
Re-evaluation of morphological structures and elemental constitution of lesions is critical to differential diagnosis. In the case examined here, the identification of post-mortem structures rules out the former diagnosis of Langerhans-cell histiocytosis. Re-evaluation of cases of rare diseases require applying a range of methods during the analysis, as every single case makes a difference in the numbers of this very small group of diseases.
This study emphasizes the importance of utilizing different analytical techniques to avoid false diagnoses.
Not all morphological features can reliably be diagnosed using microscopic and elemental techniques.
In the case of rare diseases that are difficult to diagnose, the widest possible spectrum of techniques should always be used, particularly microscopy.

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