A rare presentation of a young adult with Lambert-Eaton myasthenic syndrome and respiratory distress: Case report

Abstract

Background

Lambert-Eaton myasthenic syndrome (LEMS) is a rare condition characterized by proximal muscle weakness, autonomic symptoms, reduced tendon reflexes, the presence of pathogenic autoantibodies to P/Q-type voltage-gated calcium channels, and repetitive nerve stimulation abnormalities. Non-specific symptoms and coexisting organ-specific autoantibodies can be misleading.

Case report

A 24-year-old male patient with a history of autoimmune thyroid disease presented with proximal muscle weakness and weight loss. Electromyography and muscle biopsy showed signs of myopathy. The presence of anti-OJ antibodies and ground glass opacities suggested anti-synthetase syndrome. Plasmapheresis, corticosteroids, mycophenolate mofetil, and tacrolimus were started. His clinical condition improved, but muscle strength did not fully recover. Three years later, his muscle strength declined and he developed diplopia, areflexia, autonomic dysfunction, and respiratory failure. In this critically ill and frail patient, multitargeted therapy with plasmapheresis, corticosteroids, and mycophenolate mofetil was started in combination with eculizumab. Anti-voltage gated calcium channel seropositivity then proved LEMS, whereafter amifampridine, pyridostigmine, and rituximab were added. His condition improved. No malignancy or genetic cause was found.

Conclusion

We report a case of non-tumour LEMS in a young patient with autoimmune comorbidities (Graves’ hyperthyroidism and anti-synthetase syndrome), respiratory symptoms, and initial signs of myopathy, leading to a substantial diagnostic delay. This critically ill patient responded well to multitargeted immunotherapy in combination with amifampridine and pyridostigmine. This case illustrates the diagnostic challenges in this rare presentation.