Purpose: The Kii Peninsula of Japan, together with Guam and West New Guinea, has one of the highest incidences of amyotrophic lateral sclerosis (Kii ALS) in the world. There is a controversy whether the etiology is the same or not between sporadic ALS and Kii ALS. Skin studies from patients with sporadic ALS have shown unique pathological and biochemical abnormalities. However, there has been no report of collagen content of the skin of Kii ALS patients. Methods: The skin tissues from Kii ALS patients were studied by electron microscopy and their collagen contents were examined.

Results: On electron microscopy the most conspicuous finding in Kii ALS was the smaller diameter of collagen fibrils. The collagen content per dry weight (mg) of the samples in Kii ALS was significantly decreased (p< 0.001) than in controls. In Kii ALS patients the more severely affected pathological samples showed the greater decrease. In addition, there was a significant negative correlation (r=-0.88, p< 0.01) between the collagen content and duration of illness in the Kii ALS patients, but there was no such correlation in controls.

Conclusion: These results indicate that the metabolism of skin collagen might be affected in the disease process of Kii ALS.