WordNet records no synonym and no antonym for infantile autism. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a rare but serious syndrome of childhood characterized by withdrawal and lack of social responsiveness or interest in others and serious linguistic deficits
“there is considerable dispute among specialists concerning infantile autism”
Synonyms, antonyms and the broader and narrower relations for infantile autism come from Princeton University’s WordNet. Full sources and licences.