Autoimmune Myasthenia Gravis in Preschool-Aged Children: Report of Three Cases

Background: Myasthenia gravis (MG) is a rare autoimmune disorder of the neuromuscular junction in young children, with onset before five years of age being particularly uncommon. In the pediatric population. Diagnosis relies on clinical evaluation, antibody testing, neurophysiological studies, and imaging to assess for thymic abnormalities. Management includes pyridostigmine, corticosteroids, and other immunosuppressive therapies. We report three cases of early-onset autoimmune MG to illustrate clinical variability, diagnostic challenges, and therapeutic strategies. Case presentations: Case 1 involved a 4-year-old female presenting with fluctuating bilateral ptosis, diplopia, facial weakness, and generalized fatigability. Electrophysiological studies supported postsynaptic neuromuscular junction dysfunction. Anti-acetylcholine receptor (AChR) and anti-muscle-specific kinase (MuSK) antibodies were negative, the genetic panel for congenital myasthenia was unremarkable, and chest imaging was normal. She was initially treated with pyridostigmine and prednisolone, with azathioprine introduced after disease relapses. She subsequently experienced a myasthenic crisis requiring PICU admission and intravenous immunoglobulin (IVIG), achieving complete recovery. The patient became asymptomatic at 12 years and 3 months of age while on pyridostigmine and has been off all treatment since age 14. Case 2 was a 2-year-old female presenting with intermittent bilateral ptosis and preserved ocular motility. Anti-AChR and anti-MuSK antibodies were negative, and metabolic and genetic studies were unremarkable. The patient, treated with pyridostigmine, has been asymptomatic since 3 years and 3 months of age and off treatment since 4 years and 7 months of age. Case 3 involved a 2-year-old male with intermittent ptosis progressing to bilateral involvement. Anti-AChR antibodies were weakly positive, chest CT was normal, and electromyographic study could not be performed due to poor tolerance and the complexity of the technique. Treatment with pyridostigmine and a short course of prednisolone resulted in clinical improvement. The patient has been asymptomatic since 3 years of age, off treatment since 4 years and 3 months of age, and was discharged from follow-up at 6 years and 4 months. Conclusion: Myasthenia gravis with onset before five years of age is rare and poses significant diagnostic challenges. In this series, three children presented with fluctuating ptosis and fatigability—two with isolated ocular manifestations and one with generalized weakness. Two patients were seronegative, and two had negative genetic testing for congenital myasthenic syndromes. Clinical improvement was achieved with pyridostigmine and corticosteroids, with one child requiring long-term azathioprine. Only one experienced a myasthenic crisis requiring intensive care. These cases highlight the clinical heterogeneity of early-onset myasthenia gravis and emphasize the importance of prompt recognition, genetic exclusion of congenital syndromes, and individualized immunosuppressive management. Although electromyographic studies represent the standard method for objectively assessing neuromuscular junction dysfunction, their use in preschool-aged children is constrained by the poor tolerance of this population to neurophysiological techniques.