Phenotypic patterns and response to immunotherapy in a group of Very Late Onset Myasthenia Gravis: a single center study.

Background/aims: The goal of this study was to assess the clinical profile of myasthenia gravis (MG) in patients diagnosed above 65-years of age (VLOMG) and identify clinical/serological parameters associated with their MG status and prognosis.

Methods: This was a retrospective assessment of consecutive patients with VLOMG (n = 70) Demographics, clinical characteristics, medical comorbidities, the Myasthenia Gravis Foundation of America (MGFA) severity scale scores, and MGFA Post-Intervention Status (MGFA-PIS) were collected.

Results: The research population was diagnosed with MG at an average age of 73.16 ± 6.33 years, a male/female ratio of 2.3/1 and a mean follow-up time of 53.09 ± 46.37 months. The titer of acetylcholine receptor antibodies (AChR Abs) was positive at 95.71% of patients. The predominant distribution of myasthenic weakness was oculobulbar (63.79%). At the last follow-up, 75.71% of patients reached Pharmacological-Remission (PR) or Minimal-Manifestations (MM), 17% manifested improvement and 7.14% were clinically unchanged, worse or dead, according to MGFA-PIS. Most patients responded to low doses of steroids. Males and patients with generalized muscle involvement upon disease-onset were more likely to reach PR or MM than females or ocular presentation (OR = 3.84 and O.18, respectively). Six patients (8.57%) were treated with at least one cycle of rituximab due to disease severity. Five (83%) reached PR or MM and one improved (mean follow up time: 7.5 months).

Interpretation: We found that patients with VLOMG are usually males, with oculobulbar muscle involvement and positive titer of AChR Abs. The majority had a favorable prognosis and an adequate response to low doses of prednisolone and long-term immunosuppression.