GENERALIZED JUVENILE MYASTHENIA

Autoimmune myasthenia in children and adolescents, traditionally named as juvenile myasthenia, is characterized by fluctuating weakness and fatigue in ocular, facial, bulbar or limb muscles. Pure ocular presentation is common, and progression to generalized myasthenia in these cases is less frequent than described in adults. The phenotype associated with muscle-specific kinase antibodies: marked bulbar and respiratory involvement is probably rare in children and was absent in our series (n=30) followed-up for 2–20 years. Acetylcholine receptor antibodies were present in half of the ocular and 70% of the generalized cases at presentation. Initially antibody-negative ocular cases can develop mildly elevated titers in 1–5 years without manifesting more widespread or more severe disease. The highest and constantly elevated antibody titers are observed in peripubertal girls. Spontaneous remissions are not rare (8% of ocular and 27% of generalized cases in our series), particularly in children with onset before 10 years of age. These figures may vary according to the length of follow-up.

The diagnosis of juvenile myasthenia is confirmed by electromyography (EMG), single fiber EMG, and clinical response to anticholinesterase medication. Treatment methods include anticholinesterase drugs, thymectomy, and immunomodulator agents; plasmapheresis and intravenous immunoglobulin are used in myasthenic crisis. The differential diagnosis includes congenital myasthenic syndromes, characterized by (usually) infantile onset, family history, and lack of clinical response to immunomodulatory treatment. According to our findings, juvenile myasthenia of pre-pubertal onset is relatively benign, and clinical remission is achieved in the majority of patients with the current treatment methods.