BACKGROUND AND OBJECTIVES

Juvenile myasthenia gravis (JMG) is a rare disorder defined as MG in patients younger than 18 years. Generalized JMG is more common in postpubertal than prepubertal patients. There are no formal international JMG treatment guidelines, and knowledge on treatment patterns and disease burden is limited. The aim of this study was to describe treatment patterns and health care resource utilization (HCRU) for patients with JMG and explore differences in disease presentation between prepubertal-onset (younger than 12 years) and postpubertal-onset (12-17 years) patients.

METHODS

Patients with JMG, newly diagnosed from 2008 to 2021, were identified from the US Merative MarketScan® Research Databases. Patients were followed from the first JMG claim (diagnosis/treatment with acetylcholinesterase inhibitors, immunoglobulin [Ig], or plasma exchange [PLEX]). The primary outcome was JMG-related treatment changes during follow-up, assessed descriptively. Rates of MG exacerbation, thymectomy, and acute intravenous immunoglobulin/PLEX treatment were assessed. HCRU was evaluated.

RESULTS

A total of 630 patients (64.1% female; mean [SD] age 9.07 [5.73] years; 57.6% prepubertal onset) were followed for a median (range) of 2.4 (0-13) years. Corticosteroids were started at a median (range) of 1.28 (0-37.02) and 3.19 (0-87.68) months from diagnosis for postpubertal-onset and prepubertal-onset patients, respectively. The rate of thymectomy was highest during treatment with maintenance Ig/PLEX (incidence rate [IR]; [95% CI] per 100 patient-years: 34.62 [14.41-83.17] for postpubertal-onset and 24.24 [9.10-64.60] for prepubertal-onset patients). MG exacerbations were most frequent during the first year of follow-up in both subgroups (34.1% and 30.3%). In postpubertal-onset patients, exacerbation was highest during treatment with maintenance Ig/PLEX and nonsteroid immunosuppressant therapy ([NSIST], mostly polytherapy) (IR [95% CI] 105.81 [68.99-162.29] and 91.22 [65.80-126.47]). For prepubertal-onset patients, exacerbation was most frequent during NSIST (polytherapy) and biologic treatment (IR [95% CI] 140.44 [115.45-170.85] and 142.95 [46.10-443.23]). JMG-related hospitalizations occurred in 36.0% and 30.0% of postpubertal-onset and prepubertal-onset patients, in the first year of follow-up.

DISCUSSION

Patients with JMG escalated rapidly through the treatment hierarchy. Postpubertal-onset patients escalated more quickly to later-line treatments than prepubertal-onset patients. However, some patients continued to experience high HCRU, highlighting the need for new JMG treatments to provide rapid disease control. A limitation is that treatment escalation reasons were not evaluated.