A rare presentation of myasthenia gravis

Abstract

Background and aims Myasthenia gravis (MG) is a heterogeneous disorder in which antibodies are directed at the postsynaptic membrane of the neuromuscular junction, leading to varying degrees of muscle weakness and fatigability. Ptosis, dysphagia, dysphonia and proximal weakness are common presenting symptoms in children. We report a case of 14 months old male child presenting with inspiratory stridor resembling group. Methods and results A 14 months old child presented to accident and emergency (A&E) of a district general hospital for the third time in a week, with barking cough, noisy breathing and stridor. His symptoms had worsened over the last 24 hours resulting in a choking episode and difficulty in feeding. This was preceded by a week9s history of cough, cold, diarrhoea and vomiting. He was treated as croup on first two attendances in A&E. He was born at term by normal vaginal delivery to unrelated Caucasian parents. He was diagnosed with laryngomalacia at two months of age, when he presented to paediatric outpatients for noisy breathing. This improved by 6 months of age. There was no family history of neuromuscular disorders. Examination revealed tachycardia, signs of respiratory distress, stridor, drooling from mouth and drooping eyelids. He was transferred to tertiary centre for intensive monitoring and further investigations. His initial treatment based on a presumptive diagnosis of croup did not show any response. Further investigations included MRI brain which was normal. After a failed extubation, he was subjected to tensilon test to which a partial response was noted. He was commenced on pyridostigmine and prednisolone. Repetitive nerve stimulation and stimulated single fibre electromyography confirmed the diagnosis of MG. Acetyl choline receptor antibodies were undetectable. Results of genetic screening are still awaited. Prednisolone was weaned in next 4- 6 months. He remains well on pyridostigmine. Conclusion Myasthenia gravis can present with involvement of any muscle innervated by cranial nerves and the diagnosis should be entertained when muscular weakness or fatigability is demonstrated. Although an uncommon cause Myasthenia gravis should be included in differential diagnosis of stridor.