1 Type III, also called Kugelberg-Welander disease or juvenile spinal muscular atrophy, begins to affect kids as early as 18 months of age or as late as adolescence. This is the mildest form of SMA in children.  Type IV is the adult form of the disorder.
Minamata disease, sometimes referred to as Chisso-Minamata disease, is a neurological syndrome caused by severe mercury poisoning. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision and damage to hearing and speech.
Since this is in the Japan in WW2 Category, the simplest answer would be, it got hit by a Nuclear Bomb. If you like reading books about these sort of things, there is a Manga [Japanese Comic] Series called Barefoot Gen, it is based on a true story as the Author was in Hiroshima at the time of the bombing. Hiroshima was one of two cities in Japan to be hit with an Atomic bomb during World War 2. This was one of the final acts by the United States as Japan withdrew from the war shortly thereafter.