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

• Published in: Muscle & nerve Vol. 69; no. 5; pp. 637 - 642
• Main Authors: Sechi, Elia, Deiana, Giovanni A., Puci, Mariangela, Zara, Pietro, Ortu, Enzo, Porcu, Caterina, Carboni, Nicola, Chessa, Paola, Ruiu, Elisa, Nieddu, Arianna, Tacconi, Paolo, Russo, Antonello, Manca, Davide, Sechi, M. Margherita, Guida, Melania, Ricciardi, Roberta, Ercoli, Tommaso, Mascia, Marcello M., Muroni, Antonella, Profice, Paolo, Saddi, Valeria, Melis, Maurizio, Cocco, Eleonora, Spagni, Gregorio, Iorio, Raffaele, Damato, Valentina, Maestri, Michelangelo, Sotgiu, Stefano, Sotgiu, Giovanni, Solla, Paolo
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-05-2024; Wiley Subscription Services, Inc
• Subjects: AChR‐IgG; Confidence intervals; Epidemiology; IgG antibody; Immunoglobulin G; incidence; Kinases; MuSK‐IgG; Myasthenia gravis; Neurology; Neuromuscular junctions; Neurotransmitters; Population studies; prevalence; Receptors; Risk; Standardization; Tyrosine; World population; MuSK-IgG; prevalence; risk; incidence; AChR-IgG
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/mus.28077

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.