Co-occurrence of voltage-gated calcium channel and acetylcholine receptor antibodies: case report

Abstract

Background: Voltage-gated calcium channels (VGCC) antibodies are generally associated with Lambert Eaton myasthenic syndrome (LEMS). Their coexistence with acetylcholine receptor (AchR) antibodies, which are specific for myasthenia gravis (MG), is extremely rare. Material and methods: Analysis of one case of co-occurrence of VGCC antibodies and AchR antibodies. Results: A 36-year-old female without myasthenic symptoms underwent thoracoscopic surgery after a coincidental diagnosis of thymoma (WHO type B2). Two years later she developed generalized muscle weakness (that improved slightly after exercise), dyspnea, diplopia, blepharoptosis, dysarthria and disphagia. Electrophysiological studies showed a 20% decrement. AchR antibodies were positive (32.1 nmol/l), anti-MuSK antibodies were negative while anti-type T VGCC antibodies were atypically positive (14.51 index). The patient received pyridostigmine, corticosteroids, plasmapheresis, but due to a lack of improvement, cyclophosphamide was considered. While undergoing treatment, she developed a myasthenic crisis most likely triggered by SARS-CoV-2 pneumonia. Repeated thoracic imaging also showed a novel massive cystic mediastinal growth. Surgical treatment was recommended and the hystopathological exam revealed an invasive recurrent thymoma associated with a cystic mass. Conclusions: While up to 5% of patients with MG may test positive for VGCC antibodies, the clinical particularities of these patients have opened the debate whether LEMS and MG might overlap. Several other distinctive, but possibly interrelated features mark this case as unique, particularly the progression of the myasthenic crisis, the recurrence of thymoma and the associated cystic mass.