Subacute myelo-optic neuropathy

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Subacute myelo-optic neuropathy (SMON) is an iatrogenic disease of the nervous system[1] leading to a disabling paralysis, blindness and even death. Its defining manifestation was as an epidemic in Japan during the 1960s, affecting an estimated 30,000 people.[2] On August 3, 1978, the Tokyo District Court ruled that the cause of SMON is Clioquinol. Its manufacturer, Ciba-Geigy, has publicly stated that "Medical products manufactured and sold by us have been responsible for the occurrence of [SMON] in Japan, we extend our apologies."[2]

SMON was first observed and diagnosed in Sweden 1966, by the pediatrician and neurologist Olle Hansson.[3] Clioquinol was marketed as a prophylaxis to tourist diarrhoea. Dr. Olle Hansson was in the front line, fighting for a ban of clioquinol. Doctors in many countries boycotted Ciba-Geigy for many years. Not until 1985 was the pharmaceutical withdrawn. Dr Hansson died a few months later. The day of his death, May 23, is observed as the Anti-Hazardous Drug Day in several parts of the world.


  1. ^ Takasu T (November 2003). "[SMON--a model of the iatrogenic disease]". Rinsho Shinkeigaku. 43 (11): 866–9. PMID 15152488. 
  2. ^ a b
  3. ^ Hansson, Olle: Inside Ciba-Geigy, 1989

Further reading[edit]

  • Reisaku Kono, "Relation between Subacute Myelo-Optic Neuropathy (S.M.O.N.) and Clioquinol: Nationwide Survey", The Lancet, V301, I7796, January 27, 1973, pp. 171–173
  • Reisaku Kono, "The S.M.O.N. Virus Theory", The Lancet, V306, I7930, August 23, 1975, pp. 370–371
  • Reisaku Kono, Yoshigoro Kuroiwa, "Subacute Myelo-Optic Neuropathy is not a special form of multiple sclerosis", The Lancet, V320, I8292, July 31, 1982, p. 267
  • Hansson, Olle: "Inside Ciba-Geigy". IOCU 1989. ISBN 967-9973-26-3.