Amyotrophic lateral sclerosis with appearance of many skein-like inclusions in anterior horn cells.

We report an autopsy case of amyotrophic lateral sclerosis (ALS), in which an abnormally large number of skein-like inclusions (SLIs) was found in anterior horn cells. The patient was a 73-year-old man, who presented with dysarthria. His motor neuron symptoms were predominantly of the upper-neuron type, and cognitive impairment was also noted. He died of septic shock 13 months after onset of the first neurological symptoms. Autopsy revealed marked loss of upper motor neurons, severe degeneration of the pyramidal tract, mild to moderate loss of anterior horn cells, and the appearance of many SLIs, which were immunoreactive for both pTDP-43 (phosphorylated transactivation responsive DNA-binding protein of 43 kDa) and ubiquitin, in anterior horn cells. Intra-axonal pTDP-43-positive granules arranged in a bead-like fashion were also found. The appearance of pTDP-43-positive intracytoplasmic inclusions in the brain was mostly restricted to the motor cortex. An Alzheimer type tau-pathology was found mainly in the hippocampus (Braak stage III), and many argyrophilic grains were distributed in the limbic area. Atypical ALS showing a rapid clinical course associated with cognitive impairment and predominant involvement of the upper motor neurons has recently been reported. The present case shares some clinical and pathologic findings with this type of atypical ALS. The appearance of a large number of SLIs is an unusual finding. Although its pathologic significance remains unknown, it cannot simply be ascribed to the relative preservation of anterior horn cells.