Say an individual was born with uncontrollable intermittent ESP. Rather than something fairly innocuous like seeing ghosts, his ESP sees things from beyond. He'll randomly pick up stimulus from a surreal, unpleasant, parallel universe that will interfere with his perception of his own reality. This is perceived like augmented reality rather than whole sensory substitution, with the alien sensations overlaid onto the real ones. He is unable to take care of himself because of the interference in normal perceptions: he might become disoriented by vertigo due to a second gravitational pull or distracted by sudden shrieks and walk into traffic, or fail to attend hygiene when the bathroom fills with foul-smelling slime.
Although the symptoms are dramatically different and effectively untreatable (how do you close an imaginary third eye?), would doctors diagnose such a condition as a form of schizophrenia? He probably needs a caretaker and a seeing eye dog if he isn't simply confined in an institution.
EDIT: I can provide more detailed explanation of symptoms if that makes it easier to model. The visual symptoms include objects that obscure his line of vision. Learning to navigate blindfolded doesn't help because all of the senses are affected, such as gravity and touch. A loud, continuous noise would render him unable to hear anything else until it stops. Repulsive odors would cause nausea and possibly vomiting.