Medical illnesses with psychosis as a symptom

5.2 Medical psychosis The differential diagnosis of psychosis includes a wide range of nonpsychiatric medical illnesses, including: • Autoimmune: lupus, celiac disease, Hashimoto’s encephalopathy, anti-NMDA receptor encephalitis, other autoimmune encephalitides • Endocrine: thyroid disease, parathyroid disease, Addison’s disease, Cushing’s disease • Genetic: Wilson’s disease, Fabry’s disease, homocystinuria, porphyria, Huntington’s disease, Klinefelter’s syndrome, tuberous sclerosis, velocardiofacial syndrome • Infectious: encephalitis, neurosyphilis, cerebral malaria, HIV • Neoplastic: brain tumors, paraneoplastic syndrome • Neurologic: cerebrovascular lesions, cranial trauma, hydrocephalus, meningioma, multiple sclerosis • Nutritional: vitamin D deficiency, zinc deficiency, pernicious anemia, pellagra • Toxins: heavy metal toxicity

5.2.a Medi c al c auses o f psyc ho si s c an be easi l y m i ssed • Psychosis may be the first sign of a medical illness, appearing before other symptoms have developed. • Psychosis may be part of an atypical presentation of a common illness. • Psychosis may so grab the attention of patients, families and clinicians that more subtle physical signs or symptoms may be missed, or mistakenly attributed to psychosis. • Regrettably, cognitive biases may lead to premature conclusions that a patient’s psychosis has a psychiatric origin. • Also regrettably, physical exams, neurological exams and comprehensive laboratory testing is often minimized or neglected at specialized mental health care centers.

5.2.b F requenc y o f m edi c al c auses o f psyc ho si s The true frequency of medical causes of psychosis is unknown. However, the following studies suggest that medical causes of psychosis are common enough to always justify meticulous medical evaluation. • One of every eight patients admitted to a hospital psychiatric ward had medical illness that either caused or exacerbated psychiatric symptoms. 80% of those medical diagnoses were initially missed (Johnson, 1968). • After undergoing a standardized battery of medical tests, 60% of psychiatric inpatients had a previously undetected medical disease that caused or worsened their psychosis (Hall et al., 1980). • Consistently applying a standardized testing panel detected underlying medical disease as the cause of first-episode psychiatric symptoms in 60% of 100 consecutively screened individuals (Henneman et al., 1994). • In an emergency department patient sample, medical disease was the cause of psychosis in over one-third of studied cases (Etlouba et al., 2018).