The patient was a 42-year-old woman, high school graduate, married, and mother of two children. She presented to the psychiatric outpatient clinic on January 19, 2024, complaining of insomnia, thoughts that her husband was cheating on her, and irritability. The patient had no prior history of psychiatric hospitalization or psychiatric illness and reported that these symptoms began approximately ten days after experiencing a severe upper respiratory tract infection.
The patient presented to the emergency department approximately ten days ago with complaints of fever, shortness of breath, and fainting; laboratory and imaging tests resulted in a diagnosis of upper respiratory tract infection. Blood tests conducted at the time of admission revealed only a transient elevation in C-reactive protein (CRP) levels (22.85 mg/L), with no significant abnormalities in other systemic inflammation markers such as white blood cell count, ferritin, procalcitonin, or sedimentation rate. Clinical evaluation revealed normal oxygen saturation, a temperature of 38.1°C, and stable vital signs. No findings consistent with systemic inflammatory response syndrome (SIRS) criteria, such as hypotension, tachycardia, altered consciousness, or organ dysfunction, were observed. Therefore, it was concluded that the infection did not progress to systemic inflammation and remained limited to an upper respiratory tract infection. The patient was started on 200 mg cefuroxime and ibuprofen treatment. The patient returned to the emergency department due to worsening symptoms, and treatment was changed to 1000 mg amoxicillin-clavulanic acid, 200 mg ibuprofen, 30 mg pseudoephedrine hydrochloride, and 4 mg chlorpheniramine maleate.
After this, the patient believed that her husband had been replaced by someone else, stopped talking to him, and did not answer his phone calls. The patient avoided meeting with family members, did not make eye contact with her husband, and showed a marked withdrawal from social interactions. Her husband stated that the patient had undergone a major change in the last ten days, did not respond to him, and frequently said, “What did you do to my husband?”
Therefore, the patient was referred to the neurology department;
Neurological Examination: conscious, cooperative, and fully oriented.
Cranial nerve examination: Normal; no facial paralysis or visual field defects were detected. Muscle strength and tone were normal, and no motor weakness was observed. Deep tendon reflexes were symmetrical and normoactive. The Babinski reflex was bilateral negative. Light touch, pain, vibration, and position sense were normal. Finger-nose and heel-knee tests were normal, rapid, and coordinated; no dysmetria was observed. Fundus examination was normal; no papilledema was detected. No nuchal rigidity or other signs of meningeal irritation were observed.
Brain MRI including T1, T2, FLAIR, and diffusion sequences showed no acute or chronic pathology. No signal changes suggestive of demyelination, mass lesion, or limbic encephalitis were observed. The basal ganglia, thalamus, brainstem, cerebellum, and cortical structures were normal. No restriction was detected on diffusion imaging, ruling out acute ischemic events or infectious encephalopathy. Lumbar puncture was not performed due to the absence of meningeal irritation findings, neurological focal findings, consciousness fluctuations, or cognitive fluctuations, and normal MRI and EEG results. Although rare possibilities such as autoimmune encephalitis have not been theoretically ruled out, the current clinical picture does not warrant invasive evaluation in this direction.
During the neurological evaluation, a decrease in C-reactive protein (CRP) levels (CRP: 0.96 mg/L) was observed compared to the initial values obtained during the first emergency department visit (CRP: 22.85 mg/L), indicating a reduction in the inflammatory process. The patient did not undergo COVID-19 testing during emergency department visits or subsequent neurological evaluations, and no respiratory imaging findings suggestive of COVID-19 were recorded. However, the patient continued to believe that her husband had been transferred to another location. The following timeline summarizes the patient’s clinical findings and course (Fig. 1).
Clinical timeline of the patient
Psychiatric evaluation
The patient’s general level of alertness was normal. Orientation and cooperation were intact. Attention span, short-term memory, and abstract thinking were adequate. Although a structured cognitive assessment scale (e.g., MoCA or MMSE) was not administered, the cognitive processes observed during the interview were within the expected limits for her age and educational level. She exhibited an anxious mood and affect, and her appearance and self-care were consistent with her age and sociocultural level. The patient had persistent and reality-detached beliefs in the content of her thoughts, particularly regarding the replacement of her husband and daughter with fake people. There was no insight into the delusions. Psychomotor activity was normal, and no catatonic features such as mutism, negativism, or stereotypy were observed. Therefore, there was no need to administer the Bush–Francis Catatonic Rating Scale. Following the initial psychiatric evaluation, the patient underwent electroencephalography (EEG) by the psychiatric team. EEG showed normal background activity with no generalized slowing or epileptiform activity. Additionally, the patient’s previously obtained brain magnetic resonance imaging (MRI) scans were re-evaluated by a radiologist to rule out any potential organic pathologies that could cause psychotic symptoms. This second evaluation, which specifically focused on limbic encephalitis, demyelinating lesions, or other structural abnormalities, also did not reveal any pathology.
The patient, who had no history of psychiatric illness, reported that he was cheerful, active, and sociable prior to the onset of the illness and had no history of alcohol or substance abuse. Additionally, the patient had no known medical conditions or history of trauma/accidents, although he had undergone two cesarean sections in the past.
The patient exhibited delusional misidentification consistent with Capgras syndrome, and antipsychotic treatment with 3 mg/day of paliperidone was initiated. According to DSM-5 criteria, the clinical presentation was consistent with a psychotic disorder characterized by sudden-onset delusional misidentification symptoms in a patient without a prior psychiatric history. Approximately one month after treatment initiation, the patient presented for a psychiatric follow-up examination. In this second psychiatric evaluation, clinical observations and information obtained from the family indicated no improvement in the patient’s symptoms. The patient stated, “An unknown man has taken my husband’s place, and I am afraid of him” and “He is deceiving everyone, and everyone believes him.” A relative noted that these symptoms began after flu-like symptoms and that there had been no previous episodes of this kind.
Treatment was subsequently increased to 6 mg of paliperidone. According to family observations and clinical interviews, a slight decrease in the intensity of delusional beliefs was noted. Due to loss of follow-up, no post-treatment diagnostic tests or psychiatric evaluations were conducted. No adverse effects were reported during the short follow-up period; however, the short observation period limits the assessment of the drug’s tolerability.