Differential Diagnosis of Psychotic Symptoms
What causes psychotic symptoms?
There are several medical diseases and toxin exposures that can cause a person who does not have a psychotic disorder to experience psychotic symptoms. Therefore, according to Oliver Freudenreich, M.D., it is important for clinicians to eliminate other causes of psychotic symptoms before jumping to the conclusion that the patient has a psychotic disorder.1 In his article, “Differential Diagnosis of Psychotic Symptoms: Medical ‘Mimics’,” Freudenreich focuses on the secondary medical causes of psychosis.1 Oftentimes, it is difficult for clinicians to accurately diagnose a patient with the correct cause of psychosis, as there are several medical disorders that include it as a symptom.1 Therefore, several tests must be completed to achieve the correct answer. Even then, sometimes the cause of the psychosis seems to be indistinguishable from one disorder to the next.1
Medical Causes of Psychotic Symptoms
According to Freudenreich, there are several endocrine diseases that are associated with psychosis.1 First, there is thyroid disease, in the form of either hyperthyroidism or hypothyroidism. Also, steroid-producing tumors that are located in the adrenal gland, called Cushing Disease, is something needed to be considered when the patient is experiencing refractory psychosis. Freudenreich states that insulinomas also present with psychiatric symptoms, including psychosis, confusion, and other bizarre behavior that can be confused with sever psychotic disorders.1 Lastly, a pheochromocytoma is a rare, hormone-producing tumor which is characterized by its psychosis and episodic anxiety.
A couple different metabolic diseases have also been found to cause psychosis: acute intermittent porphyria (AIP) and Tay-Sachs Disease.1 AIP presents with abdominal symptoms, including constipation, and motor neuropathy, along with psychosis. Tay-Sachs is a rare disease that includes psychosis as a symptom.
Several autoimmune disorders present with psychosis as a symptom.1 For example, Freudenreich states that systemic lupus erythematosus (SLE) includes CNS symptoms, such as psychosis and seizures.1 Also, patients with Hashimoto encephalopathy and paraneoplastic syndromes also experience recurrent psychotic episodes.
Persons who travel often also present with diseases that include psychosis, such as cerebral malaria, toxoplasmosis, neurocysticercosis, and sleeping sickness.1 HIV infection and neurosyphilis are also diseases that may be connected to a patient’s travel history.1
According to Freudenreich, narcolepsy, characterized by excessive daytime sleepiness, sleep paralysis, hallucinations, and cataplexy also has symptoms of psychosis.1 This often leads to a mistaken diagnosis of schizophrenia.1 Also, head injuries can also lead to the development of psychosis, depending upon the severity, and oftentimes it will mimic schizophrenia.1
Important Secondary Causes of Psychotic Symptoms to Rule Out
An important area to focus on when a patient complains of psychosis is substance abuse and toxin exposure.1 For example, many toxins, drugs, and medications can cause psychosis but are difficult to pinpoint as the problem. Inquiring about all drugs and medications taken, including over-the-counter and herbal remedies is important to determining what might be the cause.1
Freudenreich states that ruling out secondary causes of psychosis is important as there are several different medical disorders and substances that can cause a person to experience such.1
 Freudenreich, O. (2012, December 3). Differential Diagnosis of Psychotic Symptoms: Medical “Mimics.” Psychiatric Times. Retrieved from http://www.psychiatrictimes.com/print/article/10168/2117281.
 Brownlie BE, Rae AM, Walshe JW, Wells JE. Psychoses associated with thyrotoxicosis—“thyrotoxic psychosis.” A report of 18 cases, with statistical analysis of incidence. Eur J Endocrinol. 2000;142:438-444.
 Bilgin YM, van der Wiel HE, Fischer HR, De Herder WW. Treatment of severe psychosis due to ectopic Cushing’s syndrome. J Endocrinol Invest. 2007;30:776-779.
 Benabarre A, Bosch X, Plana MT, et al. Relapsing paranoid psychosis as the first manifestation of pheochromocytoma. J Clin Psychiatry. 2005;66:949-950.
 Ellencweig N, Schoenfeld N, Zemishlany Z. Acute intermittent porphyria: psychosis as the only clinical manifestation. Isr J Psychiatry Relat Sci. 2006;43:52-56.
 MacQueen GM, Rosebush PI, Mazurek MF. Neuropsychiatric aspects of the adult variant of Tay-Sachs disease. J Neuropsychiatry Clin Neurosci. 1998;10:10-19.
 Arrojo M, Perez-Rodriguez MM, Mota M, et al. Psychiatric presentation of Hashimoto’s encephalopathy. Psychosom Med. 2007;69:200-201. Psychotic.