Gerstmann-Sträussler-Scheinker Syndrome (GSS) is an inherited prion disease characterized by midlife onset and slowly progression of cerebellar ataxia and dementia. We report a distinct phenotype of leg hyperreflexia in a Japanese family with GSS. A 38-year-old woman noticed unsteady gait at 33 years of age. Afterwards, dysarthria and writing difficulty were appeared. Her family history revealed that her grandfather and her mother had a clinical history of unsteadiness and mental changes. At 1 year after clinical onset, neurological examination showed cerebellar ataxia and leg hyperreflexia. At 4 years after onset, she suddenly developed insomnia and nocturnal howling. Her mental status disclosed marked disorientation, anxiety and irritability. Muscle stretch reflexes were increased in four extremities with Babinski's signs. Remarkable dysarthria and cerebellar ataxia were presented. Brain diffusion weighted imaging showed extensive hyperintensity signal areas in the cerebral cortex. A point mutation of the prion protein gene (PRNP) at codon 102 resulting in the substitution of proline by leucine (P102L) was identified. PRNP polymorphism exhibited homozygous methionine at codon 129 and homozygous glutamate at codon 219. She had verbal perseveration, somnolence and myoclonus of lower limbs, leading to akinetic mutism at 4 months after neuropsychiatric events. Phenotypic hallmark of our patient indicates leg hyperreflexia from an early disease course. This neurological sign differs from the previously reported clinical expression of Japanese and foreign patients with GSS (P102L). Thus, physicians should pay more attention to phenotypic heterogeneity in this prion disease.
