Ocular myasthenia gravis and risk factors for developing a secondary generalisation: description of a Spanish series

Ocular myasthenia gravis (MG) is the most common phenotype of MG at onset. A variable percentage of these patients develop secondary generalisation; the risk factors for conversion and the protective effect of immunosuppressive treatment are currently controversial.We designed a retrospective single-centre study with the aim of describing the demographic, clinical, and laboratory characteristics of a Spanish cohort of patients with ocular MG from Hospital Universitario de Albacete from January 2008 to February 2020.We selected 62 patients with ocular MG from a cohort of 91 patients with MG (68.1%). Median age at diagnosis was 68 (IQR, 52-75.3), and men accounted for 61.3% of the sample (n = 38). Most patients presented very late-onset ocular MG (n = 34, 54.8%). Binocular diplopia was the most frequent initial symptom (51.7%). The rate of progression to generalised MG was 50% (n = 31), with a median time of 6 months (IQR, 2-12.8). Female sex (OR: 5.46; 95% CI, 1.16-25-74; P= .03) and anti-acetylcholine receptor antibodies (OR: 8.86; 95% CI, 1.15-68.41; P = .04) were significantly associated with the risk of developing generalised MG.The conversion rate observed in our series is relatively high. Generalisation of MG mainly occurs during the first 2 years of progression, and is strongly associated with female sex and especially with the presence of anti-acetylcholine receptor antibodies.