Epidemiology of seropositive myasthenia gravis in Sardinia: A population-based study in the district of Sassari.

INTRODUCTION/AIMS: The global incidence and prevalence of myasthenia gravis (MG) range between 6-31/million and 10-37/100,000, respectively. Sardinia is a high-risk region for different immune-mediated disorders, but the epidemiology of MG remains unclear. We determined the epidemiology of MG with acetylcholine receptor (AChR)-immunoglobulin G (IgG) and muscle-specific tyrosine kinase (MuSK)-IgG in the district of Sassari (North-Western Sardinia; population, 325,288). METHODS: From the laboratory of the University Hospital of Sassari (reference for AChR/MuSK-IgG testing in Sardinia since 1998) and the main neurology units in Sardinia, we retrospectively identified MG patients with (1) AChR-IgG and/or MuSK-IgG positivity by radioimmunoprecipitation assay; and (2) residency in the district of Sassari. Incidence (January 2010-December 2019) and prevalence (December 31, 2019) were calculated. RESULTS: A total of 202 patients were included (incident, 107; prevalent, 180). Antibody specificities were AChR (n = 187 [93%]) and MuSK (n = 15 [7%]). The crude MG incidence (95% confidence interval) was 32.6 (26.8-39.2)/million, while prevalence was 55.3 (47.7-63.9)/100,000. After age-standardization to the world population, incidence decreased to 18.4 (14.3-22.5)/million, while prevalence decreased to 31.6 (26.1-37.0)/100,000. Among incident cases, age strata (years) at MG onset were: <18 (2%), 18-49 (14%), 50-64 (21%), and ≥65 (63%). DISCUSSION: Sardinia is a high-risk region for MG, with a prevalence that exceeds the European threshold for rare disease. Identification of the environmental and genetic determinants of this risk may improve our understanding of disease pathophysiology.

A 30-year epidemiologic survey (1974-2003) of haematological malignancies on the island of Sardinia: temporal changes in incidence and a geographic comparison of incidence rates.

In a previous survey of newly diagnosed haematological malignancies (HMs) in Sardinia from 1974 to 1993, we observed a marked increase in the incidence of many HMs that we chiefly attributed to improvements in case ascertainment. To better define the nature of this increase, we extended the survey by an additional decade (1994-2003), applying the same previously used methods. The incidence of HMs further increased from 1994 to 2003. The incidence rate of total HMs (THMs), standardised to the world population, was 30.15 × 10(5) person-years vs. 21.58 from 1984 to 1993 and 15.26 from 1974 to 1983. The temporal variations in the incidence differed in different HMs and were correlated with the diseases clinical characteristics and the increased availability of diagnostic tools and skills in Sardinia. These observations support the hypothesis that the temporal differences in the incidence rates observed for many HMs in Sardinia over the 30-year survey period were caused by temporal differences in diagnostic efficiency rather than by disease occurrence. An important exception was the increase in non-Hodgkin's lymphoma, which represents a true increase in occurrence, similarly to most Western countries. The incidence rates of HMs already having or reaching stable values in the decade 1994-2003 were similar to those of most Western countries. No significant evidence emerged to suggest that Sardinian particularities influenced the occurrence of HMs. This study demonstrates the extent to which diagnostic efficiency can influence incidence evaluations and emphasises the importance of prolonged observation to determine the validity of incidence rates for both temporal and geographic comparisons.