Clinical and therapeutic features of myasthenia gravis in adults based on age at onset

Abstract

Objective: To describe the characteristics of patients with very-late-onset myasthenia gravis (MG).

Methods: This observational cross-sectional multicenter study was based on information in the neurologist-driven Spanish Registry of Neuromuscular Diseases (NMD-ES). All patients were >18 years of age at onset of MG and onset occurred between 2000 and 2016 in all cases. Patients were classified into 3 age subgroups: early-onset MG (age at onset <50 years), late-onset MG (onset ≥50 and <65 years), and very-late-onset MG (onset ≥65 years). Demographic, immunologic, clinical, and therapeutic data were reviewed.

Results: A total of 939 patients from 15 hospitals were included: 288 (30.7%) had early-onset MG, 227 (24.2%) late-onset MG, and 424 (45.2%) very-late-onset MG. The mean follow-up was 9.1 years (SD 4.3). Patients with late onset and very late onset were more frequently men (p < 0.0001). Compared to the early-onset and late-onset groups, in the very-late-onset group, the presence of anti-acetylcholine receptor (anti-AChR) antibodies (p < 0.0001) was higher and fewer patients had thymoma (p < 0.0001). Late-onset MG and very-late-onset MG groups more frequently had ocular MG, both at onset (<0.0001) and at maximal worsening (p = 0.001). Although the very-late-onset group presented more life-threatening events (Myasthenia Gravis Foundation of America IVB and V) at onset (p = 0.002), they required fewer drugs (p < 0.0001) and were less frequently drug-refractory (p < 0.0001).

Conclusions: Patients with MG are primarily ≥65 years of age with anti-AChR antibodies and no thymoma. Although patients with very-late-onset MG may present life-threatening events at onset, they achieve a good outcome with fewer immunosuppressants when diagnosed and treated properly.

Figure 1. Flowchart shows patients included in the study

MG = myasthenia gravis.

Figure 2. Percentage distribution of myasthenia gravis (MG) cases by sex and age at diagnosis grouped in decades

Figure 3. Clinical classification of patients with generalized myasthenia gravis (MG) at onset and after treatment

Mean follow-up of 9.1 years (SD 4.3). (A) Myasthenia Gravis Foundation of America (MGFA) clinical status at onset (before treatment) and (B) MGFA postintervention status are represented in bars for early-onset MG, late-onset MG, and very-late-onset MG. CSR = complete stable remission; I = improvement; MM = minimal manifestations; PR = pharmacologic remission; U = unchanged; W = worsening.