[Late-onset sporadic case of SPG4 (1726T>C mutant) accompanied by polyneuropathy with diabetes mellitus].

We report a 73-year-old man with SPG4. From aged 53 he had diabetes mellitus and at 64 he developed spastic paraparesis and urinary disturbance. At 70 years, he began to walk with a stick and noted abnormal sensations in bilateral feet. There was no relevant family history. Moderate spasticity with mild muscle weakness, markedly brisk tendon reflex with pathological reflexes, and mildly abnormal sensation in bilateral lower extremities, and markedly spastic gait were found. MRI showed mild C4-C7 spondylosis and L4-5 disk protrusion but no abnormality of the corpus callosum. Nerve conduction and needle EMG studies revealed various abnormalities in distal (MCV, SCV) and proximal (F-wave) peripheral nerves, but no neurogenic changes in limb muscles. We found a missense spastin gene mutation (1726T>C) that causes Leu534Pro substitution. This spastin gene mutation was novel in Japanese, but has been reported in an Italian family. The present case's neuropathy might be related to diabetes mellitus, because SPG4 is generally not associated with neuropathy. However, recent studies suggest that SPG4 patients sometimes have subclinical neuropathy, and longer disease duration may contribute to peripheral neuropathy. Further study of clinical characteristics associated with the Leu534Pro mutation will be necessary.