Abstract:A 51‐year‐old male has suffered the gradual onset of difficulty with memory, concentration and cognition at age 50. He has progressively developed severe dementia accompanied by muscle wasting and fasciculation prominent in the upper arms and shoulders and the bulbar muscles. EMG and muscle biopsy revealed denervation patterns and a CT‐scan showed moderate cerebral atrophy. Cases of presenile dementia with motor neuron disease reported in Japan have been reviewed and the possibility of a new clinico‐pathologic entity is di