A 58 year old lady presented with rapidly progressive symmetrical limb weakness over a few weeks. She had a background of WHO-B2 thymoma diagnosed in 2005 with resultant thymectomy and adjuvant radiotherapy, however relapsed with pleural metastases in 2011, requiring chemotherapy for remission. She became known to Neurological services in 2009 with acetylcholine-receptor antibody Myasthenia Gravis(MG) for which she received 6-weekly intravenous immunoglobulin, the last being 2 weeks prior to presentation. Unusually, she sustained no rapid improvement in weakness, had lost weight, and developed dysphagia. She took no myotoxic drugs. Examination revealed bulbar and diaphragmatic weakness, severe proximal greater than distal limb weakness, arreflexia, and muscle tenderness.
Serum revealed elevated calcium, LDH, and CK of 3000. Renal function, urine, and ECG were normal. CT-body was normal. Needle EMG showed small upper limb CMAPs, no change on repetitive stimulation and short duration motor units with necrotising features. MRI limbs suggested diffuse symmetrical muscle disease and resultant right vastus lateralis biopsy suggested an inflammatory necrotic myopathy with HLA1 overexpression.
Unfortunately, despite immunosuppression with intravenous methyprednisolone, our patient died from pulmonary embolism and mesenteric artery dissection. We highlight a rare case of dual paraneoplastic syndromes; MG and necrotising myopathy, related to thymoma.