Pb2199: geographic clustering of erdheim-chester disease in italy and france

Topic: 16. Myeloproliferative neoplasms - Clinical Background: Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis in which somatic mutations involving MAPK and PI3K-AKT pathways play a crucial pathogenic role. The geoepidemiology of the disease is still unknown. Aims: Our study aimed at assessing the geographic origin of adult ECD patients in Italy and France. Methods:Methods (Italian cohort) - Data of 139 patients diagnosed from 1996 to 2022 were obtained from clinical charts of Italian ECD Referral Care Centres (i.e., IRCCS Meyer, Florence, and IRCCS San Raffaele, Milan) and of other Centres belonging to the Italian ECD Network (ItalECD). Patients with childhood-onset ECD (n=5), born in other countries (n=13), or lacking data (n=4) were excluded (N=117). Metrics regarding Italian Region demographics (i.e., resident adult population) were obtained from public reports produced by the Italian national institute of statistics (ISTAT) and used to normalise the number of ECD diagnoses. Methods (French cohort) - Data of 354 patients diagnosed from 1982 to 2022 were obtained from clinical charts of the French ECD Referral Care Centre (i.e., Hôpital Universitaire Pitié Salpêtrière - Charles Foix, Paris). Patients with childhood-onset ECD (n=4), born in overseas French Regions (n=5), born in other countries (n=96), or lacking data (n=11) were excluded (N=238). Metrics regarding French Region demographics (i.e., resident adult population) were obtained from public reports produced by the French national institute of statistics (INSEE) and used to normalise the number of ECD diagnoses. Methods (statistical analysis) - The test described and validated by Ohno Y et al. to assess significance for geographic clusters of disease (Int J Epidemiol. 1979;8(3):273-80) was used to analyse observed clustering of ECD diagnoses in Italian and French Regions. The number of diagnoses per 1’000’000 adult residents for each Region was classified according to their ratio over national average, which was taken as 100: (1) above national average ratio (>120), (2) in line with national average ratio (80-119.9), (3) below national average ratio (<80). Results: The Italian Regions showing a frequency of ECD diagnoses over national average (i.e., 2.35/1’000’000 adult residents) clustered in Southern Italy (Fig. 1A), whereas French Regions exhibiting a rate of diagnosis over national average (i.e., 4.68/1’000’000 adult residents) clustered in the central area of the country (Fig. 1B). Statistical analysis demonstrated that such geographic aggregations were statistically significant (P-value < 0.01 for Italy and < 0.05 for France). Summary/Conclusion: The significant geographic clustering of ECD diagnoses, with higher incidences in Southern Italy and central Regions of France, suggests the potential role of genetics and/or environmental exposures in the development of the disease. Further epidemiological studies are required to highlight specific risk factors.Keywords: Myeloid malignancies, Risk factor, Macrophage, Epidemiology