• Krabbe’s disease
• globoid cell leukodystrophy
• myelopathy

A 55-year-old man reported progressive unsteadiness affecting both legs for 2 years. He dragged both feet while walking and felt the right leg was weaker than the left. He had occasional lower back pain and tingling down the lateral aspect of his right leg, but no sciatica. He reported erectile dysfunction but without sphincter disturbance or saddle numbness. There were no cranio-bulbar, upper limb or behavioural complaints, and no weight loss or other constitutional symptoms.

He had been born at term to unrelated and healthy parents. There had been no perinatal complications and he attained normal developmental milestones. He had hypertension, reflux oesophagitis and an umbilical hernia repaired 1 year before. His medications included diltiazem, simvastatin, ezetimibe, esomeprazole and co-codamol. He did not smoke and drank less than 14 units of alcohol per week. He did not use illicit drugs.

He had three siblings. A brother had developed walking difficulty when aged 52 years and had been diagnosed with progressive multiple sclerosis; he later committed suicide. We did not have access to the brother’s case notes. His other siblings were healthy.

On examination, the cranial nerves, upper limb motor, sensory and cerebellar examinations were normal. He had spasticity in both lower limbs especially on the right. There was mild bilateral weakness of hip flexion, but otherwise normal muscle strength. Reflexes in both lower limbs were pathologically brisk with crossed adductors bilaterally and 2–3 beats of clonus in both ankles. His plantars were bilaterally upgoing. There was mildly reduced pinprick sensation in both feet up to the ankles, but vibration and joint-position sense were normal. He struggled to walk tandem but there were no other cerebellar signs and no extrapyramidal features. Romberg’s sign was negative.