Objective: Analyze the clinical presentation, laboratory indicators, and outcome of patients with late-onset myasthenia gravis (after 60 years).
Method: This retrospective cohort design with prospective follow-up included 45 patients with late-onset myasthenia gravis diagnosed in hospitals in Avignon, Montpellier, and Nimes between 1993 and 2000. Prospective data collection of their subsequent course took place in 2001.
Results: Median age at onset was 72 years and median follow-up 35.5 months. Initial symptoms were ocular (38/45, 95%) and bulbar (31/45, 69%). Initial Osserman grades were distributed as follows: 10 grade I, 2 grade IIA, 25 grade IIB, 8 grade III and no grade IV. Anticholinesterase antibodies were positive in 39 patients (91%), response to anticholinesterase positive in 31/33 (94%), and electrophysiological abnormalities observed in 20/33 (61%). Thoracic computed tomography, performed in 42 patients (93%), found thymic abnormalities in 7. At least one comorbid disease was diagnosed in 41/43 patients (93%) and an autoimmune disorder in 18/43 (42%). In all, 42 patients (93%) received anticholinesterase and 36 (80%) immunosuppressive therapy. Sixteen patients (36%) died during follow-up, 8 of causes directly related to the myasthenia gravis. The relative risk of death estimated by odds ratios (OR) was highest for patients with comorbid cancer (OR 8.6 [1.8-40.6]) and those with the highest Osserman scores: grades I-II OR: 0.05 [0.01-0.29] versus grades III-IV OR: 15.5 [2.9-83.0].
Conclusion: Late-onset myasthenia gravis is specific in many aspects (presentation, autoimmune and other comorbid conditions, and course) that require attentive care.