A 90 year old man presented with progressive dysphagia, generalised weakness, and malaise. He had lost 30 lb (13.6 kg) in the past six months, and his mobility had deteriorated because of progressive leg weakness. He had no visual or constitutional symptoms apart from weight loss and denied any bladder or bowel problems. He had a 25 pack year history of smoking and did not drink alcohol. Examination showed signs consistent with bilateral pneumonia. His speech was dysphonic, the gag reflex was absent, but other cranial nerves were intact. He had wasting and weakness of the small muscles of the hands and weakness of the proximal muscles of the lower limbs. Reflexes were absent in the lower limbs. Strength in the remaining muscle groups—including ankle dorsiflexion, planter flexion, knee extension, and flexion—was normal. Proximal muscle groups in the upper extremity were strong, although reflexes were reduced bilaterally. No fasciculations were seen and he had no evidence of fatigable ptosis. Sensory examination was normal. Examination of the cardiovascular and abdominal systems was unremarkable. Investigations showed a white blood cell count of 5.9×109 cells/L (reference range 4.0-10.0), haemoglobin 117 g/L (140-180), platelets 332×109 (320-360), random glucose 10.8 mmol/L (3.6-11), urea 25.3 mmol/L (3.0-7.1), creatinine …