A 66-year-old woman gave a 6-year history of progressive weakness. Her initial symptoms were aching hips, shoulder pain and difficulty getting out of a chair. A rheumatologist diagnosed polymyalgia rheumatica—despite significant weakness—and gave prednisolone for several months. Despite initial improvement, her weakness slowly progressed until she could not climb stairs or walk a reasonable distance. At the time of presentation, she reported anorexia with 4 kg weight loss over 6 months and recent suprapubic swelling. She had difficulty raising her arms above her head, and problems with chewing and swallowing. There were no sensory symptoms, diplopia or difficulty breathing, and no change in cognition or behaviour.

She had been diagnosed with breast cancer around the same time as polymyalgia rheumatica, and had undergone lumpectomy, radiotherapy and hormone therapy with curative intent. Two years before her current presentation, she developed a subacute bowel obstruction requiring colonoscopy; the surgical specimen showed bowel/sigmoid amyloid. Repeat colonoscopy a year later was normal. She also had a melanoma resected 10 years before.

There was a family history of early onset dementia with prominent behavioural abnormalities in her sister, mother, maternal siblings and maternal grandmother. Her own two daughters were well.

On examination, her blood pressure was 110/80 mm Hg lying and 90/70 mm Hg standing; other vital signs were normal. She had a protuberant abdomen with divarication of the rectus muscles and significant suprapubic pitting oedema. Her tongue was large. There was shoulder girdle wasting, with occasional fasciculations in the deltoid, trapezius, biceps and triceps muscles, and mild weakness of shoulder abduction, neck flexion and left wrist flexion. Her reflexes were all brisk. There was quadriceps wasting with occasional fasciculations and mild proximal hip flexor weakness. Her reflexes were brisk with one beat of clonus and her plantar responses were downgoing.