Childhood Ocular Myasthenia Gravis

Purpose: To investigate the clinical manifestations and ocular findings in children with ocular myasthenia gravis (MG) that rarely have been reported in the literature.

Design: Retrospective, noncomparative case series.

Participants: Twenty-four consecutive patients less than 15 years of age with ocular MG treated between June 1988 and July 2001.

Methods: The medical records of 6 boys and 18 girls with ocular MG were reviewed retrospectively.

Main Outcome Measures: Alternate prism cover and uncover test, examination of ductions and versions, and visual acuity.

Results: Mean age at onset was 38 months. Ptosis was found in 23 patients (96%), strabismus in 21 patients (88%), and amblyopia in 5 patients (21%). Exotropia combined with vertical heterotropia was the most frequent type of strabismus. Ductions were limited in 17 patients (71%), among whom supraduction or infraduction limitations were most frequently observed. Contrary to previous reports, medial rectus underaction was less common than lateral rectus underaction. Manifestations of strabismus and limitation of duction were variable and changed frequently during the follow-up period. The combined use of prednisone and pyridostigmine was found to be the predominant form of maintenance therapy, and ptosis was more responsive to drug therapy than limited ocular motility.

Conclusions: Children with ocular MG were found to have a high incidence of ptosis (96%) and exotropia and vertical hyperdeviation. Limitation on adduction was less common than that on abduction. First reported incidence of amblyopia (21%) and a relative nonresponsiveness of the limitation of eye movement to treatment were also noted.