This is a case report of hypochondrical paranoia in a young man, who was convinced of a toxic infection by fungi following mold growth exposure. The patient was admitted to a psychiatric facility, severely pained by the delusional perception of his insides being eaten by fungus. He had undergone a thorough medical examination without the discovery of any somatic irregularities and had attempted to treat himself several times. After four months of hospital-ization and the prescription of antipsychotic treatment, he was in recovery. Mild delusions persisted but were no longer pathologically painful.