Myasthenia gravis in childhood

Pathologic alterations in neuromuscular transmission, known as Myasthenia Gravis (MG), comprise combinations (forms) of pre- and post-synaptic changes whose age at onset and clinical manifestations are dissimilar. Some forms have autoimmune features, while others have a defect due to functional or structural plaque alternations. The purpose of this work is to describe the clinical forms of MG seen in childhood, to facilitate proper diagnosis and treatment.

Retrospective data from 87 patients studied at the Ricardo Gutierrez Children's Hospital from 1990 to 2002 are presented. They were evaluated by clinical, pharmacological, electrophysiological, laboratory and radiological exams.

Three distinct groups of patients were found: Group 1, Transient Neonatal Myasthenia Gravis (TNMG) represented 6.8% 9 (n=6) of the total number of patients. None of these six patients had ocular involvement. Group 2, Congenital Myasthenia (CMG) represented 17.2% of cases 9 (n=15). These patients had an onset of symptoms from 1 to 12 months of age. Eight cases were sporadic and the remainder familial. The most frequent symptom in this group was bilateral blepharoptosis in 13 patients. Group 3, Juvenile Myasthenia (JMG) comprised 76% of the patients (n=66). The onset of symptoms in this group ranged from 13 months to 14 years (mean 3.6 years). Thirty-nine of these children presented purely with ocular symptoms.

Children with myasthenia gravis may present to the ophthalmologist first, with symptoms such as unilateral or bilateral blepharoptosis, diplopia, strabismus or ophthalmoplegia. Therefore, it is essential that the ophthalmologist be aware of the varied features of this disorder in children in order to diagnosis it correctly and make appropriate treatment referrals.