A previously healthy man in his sixties presented with a 10-year history of progressive symmetrical and proximal lower extremity weakness, muscle atrophy, and fasciculations without any pain or sensory symptoms, which had spread gradually to his proximal upper extremities. Recently he had also noted weakness in his left hand causing difficulty clipping his nails. In addition, he had a five-year history of slurred speech without any difficulty swallowing. He had had mild dyspnoea on exertion and moderate low back pain for years. He denied any muscle pains or cramps, or any cognitive, cranial, bowel or bladder symptoms. He had been diagnosed with progressive muscular atrophy two years previously and came to our clinic for continuity of care. He had borderline diabetes and hypertension, but was otherwise well. There was no family history of any neuromuscular disorder, and he did not smoke or drink alcohol.

The abnormal neurological signs included mild bifacial weakness involving eye closure, mild dysarthria, and frequent perioral and tongue fasciculations with atrophy. There was mild weakness with atrophy in both lower extremities proximally and distally, the left hand, and neck flexion along with minimal weakness with atrophy in his proximal upper extremities with occasional fasciculations. He had depressed reflexes, no Babinski sign on either side, and sensation was normal. There was mild gynaecomastia.

Routine blood tests were normal, and urine heavy metal screen was negative. ANA was slightly raised at 1:160. Plasma CPK was raised at 2122 U/l (normal range 0–175 U/l). Nerve conduction studies (NCS) were normal. Electromyography (EMG) showed active denervation and reinnervation in the right arm and leg muscles proximally and distally, and spontaneous activity in the right thoracic paraspinal muscles. There were signs of reinnervation without active denervation in the right genioglossus. A spinal MRI was unremarkable. A left vastus lateralis muscle biopsy …