Subacute myelo-optico-neuropathy (SMON) is a disease characterized by subacute onset of sensory and
motor disorders in the lower half of the body and
visual impairment preceded by abdominal symptoms. A large number of SMON were observed throughout Japan, and the total number of cases reached nearly 10,000 by 1970. Despite clinical features mimicking
infection or
multiple sclerosis, SMON was confirmed as being caused by ingestion of
clioquinol, an intestinal antibacterial
drug, based on extensive epidemiological studies. After the governmental ban on the use of
clioquinol in September 1970, there was a dramatic disappearance of new case of SMON. In the 1970s, patients with SMON initiated legal actions against the Government and
pharmaceutical companies, and the court ruled that the settlements would be made as health management allowances and lasting medical check-ups. The physical condition of patients with SMON remains severe owing to SMON as well as gerontological complications. The pathological findings in patients with SMON included symmetrical
demyelination in the lateral and posterior funiculi of the spinal cord and severe
demyelination of the optic nerve in patients with
blindness. Although
clioquinol may show activity against
Alzheimer's disease or
malignancy, its toxic effects cause severe irreversible neurological sequelae. Thus, caution must be exercised in the clinical use of
clioquinol.