Subacute myelo-optico-neuropathy (SMON) in Japan. With special reference to the autopsy cases

Subacute myelo-optico-neuropathy (SMON) is a predominantly sensory neuropathy with peculiar clinical and histopathological features which began to appear in Japan around 1960, continued to increase and reached the highest annual incidence of 2,814 in 1959. Clioquinol or chinoform was strongly suspected as the cause of the disease because the iron chelate of chinoform was identified in the green urine of the patients. It is now believed that chinoform is the cause of SMON for the following reasons: 1) The retrospective investigation indicated that the majority of SMON patients had been given chinoform. 2) Dogs and monkeys orally given chinoform for many days in plural institutions showed exactly the same degenerative changes in the posterior and lateral funiculi of the spinal cords as the human patients. One institution obtained the same lesions also in cats. 3) The number of new patients has greatly decreased after the production and sale of chinoform were banned in September 1970. The pathology of the SMON patients and experimental chronic chinoform intoxication in animals were reviewed with some etiological comments.