In addition to the acute schizophreniform psychosis described earlier, the authors have encountered the greatest difficulties in the diagnosis of schizophrenia in the following clinical situations: 1. A patient with a healthy family and premorbid history with an acute illness having many of the typical features of schizophrenia but associated with confusion, forgetfulness, and/or clouding of consciousness. Thus the illness combines the features of schizophrenia and a confusional state. This syndrome is characteristic of  autoimmune encephalitis, particularly a form caused by anti-NMDA antibody (Chap. 30), of hallucinogenic drug use, particularly phencyclidine intoxication, corticosteroid psychosis (drug-induced or Cushing disease), and thyrotoxic psychosis. Usually recovery is complete with appropriate treatment, and schizophrenia is excluded by the fact that the patient remains well.
2. Adolescents and young adults whose social relationships are disorganized and who are unusually sensitive, resentful, rebellious, fearful, discouraged, in trouble with school authorities and the law, and using drugs. Such patients may be classified as having a borderline personality or “sociopathy” that appears to go back several years. These types of personality disorders and social maladjustments turn out not to be schizophrenia.
3. There is another related type of diagnostic problem, arising in an individual who has been only marginally competent because of personality problems and many vague neurotic and hypochondriacal symptoms, often requiring prolonged psychotherapy. Many such individuals will indeed be found to have simple schizophrenia (so-called pseudoneurotic form).
4. In a chronic delusional-hallucinatory state in a chronic alcoholic patient (chronic alcoholic hallucinosis) it will usually be disclosed that the illness began when alcohol was withdrawn, after a period of sustained drinking, and at first took the form of an acute auditory hallucinosis characterized by threatening, exteriorized auditory hallucinations to which the patient’s emotional reaction was appropriate. Only later do a few of these patients drift into a quiet hallucinatory, mildly paranoid state, with rather bland affect. Evidence of the prepsychotic schizoid personality cannot be detected and there is usually no family history of schizophrenia. Cases of this type with which we are familiar had their onset between 45 and 50 years of age, that is, much later than the usual age of onset of schizophrenia.
5. A patient who is confused or stuporous and seemingly catatonic-negativistic, refusing or unable to speak, to execute commands, or to be activated in any way. If signs of focal cerebral or brainstem disease are absent, one is tempted to make a diagnosis of catatonic schizophrenia, not appreciating that catatonia as a phenomenon may be indistinguishable from akinetic mutism (see Chap. 15). It may also appear with widespread disease of the associational cortices and as mentioned earlier, with severe depression, certain confusional states, and hysteria. The authors have seen cases of hypoxic and other metabolic encephalopathies, Schilder disease, certain storage diseases, and Creutzfeldt-Jakob disease mistaken for schizophrenia because of failure to adhere to this principle.
6. A patient with temporal lobe epilepsy who, apart from intermittent psychomotor seizures, has long periods (weeks or months) of hallucinations, delusions, bizarre behavior, and disorganization of thinking. Such a mental disturbance reflects the presence of a persistent state of temporal lobe seizures (temporal lobe status epilepticus), which in some cases has been demonstrated by depth electrodes to originate in the amygdaloid or other medial temporal areas. The nature of the disturbances of emotionality and mentation in such patients, a somewhat controversial subject, is discussed in Chaps. 15 and 24.