Medical Mimics: Differential Diagnostic Considerations for Psychiatric Symptoms

Ment Health Clin. 2016 Nov 3;6(6):289-296. doi: 10.9740/mhc.2016.11.289. eCollection 2016 Nov.


Patients with underlying medical disease can present to the health care system with psychiatric symptoms predominating. Identification of an underlying medical condition masquerading as a psychiatric disorder can be challenging for clinicians, especially in patients with an existing psychiatric condition. The term medical mimic or secondary psychosis has been used to describe this clinical situation. Diagnostic categories from The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, that may encompass medical mimics include substance-induced disorders, which includes medications, and unspecified mental disorder due to another medical condition in situations where the clinician may lack needed information for a complete diagnosis. At this time, there is no single diagnostic test or procedure available to differentiate primary versus secondary psychosis on the basis of psychopathology presentation alone. When considering a diagnosis, clinicians should evaluate for the presence of atypical features uncharacteristic of the psychiatric symptoms observed; this may include changes in functionality and/or age of onset and symptom presentation severity. The purpose of this work is to provide a structured clinical framework for evaluation for medical mimics, identify groups considered to be at highest risk for medical mimics, and present common syndromic features suggestive of a medical mimic. Selected case scenarios are used to illustrate key concepts for evaluating and assessing a patient presenting with acute psychiatric symptomatology to improve judgment in ruling out potential medical causality.

Keywords: diagnostic evaluation; medical mimic; physical examination; psychotic disorder due to another medical condition; secondary psychosis; substance-induced disorder.