In contrast to adults, progression in preadolescent patients from ocular myasthenia to generalized disease is much less common, occurring in 10–15% of cases. Among 21 cases of purely ocular myasthenia treated at the Children's Hospital of Los Angeles, confirmed in all but one case by a positive edrophonium test, onset of symptoms ranged from 7–57 months of age and only 3 (15%) cases progressed to systemic disease (Ortiz, Ophthalmology 2008).
Among all pediatric myasthenia patients, about a third have only ocular disease. In Alberta, Canada, among 52 cases of juvenile onset myasthenia gravis, there were 34 cases of generalized and 18 cases of ocular myasthenia. Age at onset ranged from birth to 17 years for the generalized form and 18 months to 11 years for the ocular subtype. The rate of antibody positivity is similar to adults or slightly lower. Acetylcholine receptor antibodies were found in 67% of generalized cases and 44% of ocular myasthenia patients in the Alberta study. Response to pyridostigmine was excellent in this group, noted in 33 (100%) of 33 generalized cases and 88% of ocular cases. (VanderPluym, Pediatrics 2013)
In a study of 24 cases of myasthenia diagnosed before age 15, ptosis was present in 96% of cases (n = 23) (Kim, Ophthalmology 2003).
Among 34 juvenile myasthenia cases at The Hospital for Sick Children in Toronto, 14 patients underwent thymectomy and none had thymoma. A third of those 34 patients (n = 8) went into long term asymptomatic remission and required no further medical treatment. Half of these patients (n = 4) had undergone thymectomy (Mullaney, Ophthalmology 2000).
Response to thymectomy is variable in the pediatric population. In a study of 50 juvenile onset myasthenia patients at Children's Memorial Hospital in Chicago, 13 patients underwent thymectomy. A quarter of those patients (n = 4) had a complete remission and no further medication was needed. A quarter (n = 3) had improvement and required less medication, a quarter (n = 3) had slight improvement and required the same medication and a quarter (n = 3) showed no change. (Della Marina, Neuropediatrics 2014).
Similarly, among 39 juvenile myasthenia patients treated at the Children's Hospital of Philadelphia, complete disease resolution occurred in 25% (n = 10) within 5 years. In this cohort, thymectomy was performed in 38% (n = 15) and medical treatment involved pyridostigmine alone (38%) or in combination with steroids (49%) with 10% of patients requiring other medical treatment. (Pineles, AJO 2010).
Amblyopia associated with myasthenia has been documented in the literature. Vigilance is necessary with patching regimens and surgical intervention for ptosis and strabismus.