Free USMLE Step 2 CK Psychiatry practice questions

Lithium levels are interpreted only as 12-hour trough samples, drawn in the morning about 12 hours after the evening dose and before the morning dose. This patient's blood was drawn 3 hours after he took 600 mg, close to the absorption peak, so the value of 1.4 mEq/L overestimates his steady-state exposure and looks falsely toxic. He is clinically well: the fine postural tremor is a stable, longstanding side effect at therapeutic levels, and he has no gastrointestinal symptoms, coarse tremor, ataxia, or confusion that would suggest real toxicity. His renal function is normal, and 2 weeks after the dose change he is past the roughly 5 days needed to reach steady state. The correct next step is to repeat the level as a properly timed trough (instructing him to hold the morning dose until after the draw) and act on that result.

B. Halving the dose based on a mistimed sample risks relapse of the hypomania that prompted the increase; dose changes should follow a valid trough. C. Holding lithium and giving IV saline is the treatment for clinical toxicity, which he does not have. D. An ECG is part of baseline evaluation over age 40 or with cardiac disease and is reasonable in true toxicity, but it does not answer whether his level is actually high, and creatinine was already obtained. E. Switching to valproate abandons an effective drug that lowers suicide risk on the basis of a misleading laboratory value.

This woman has postpartum psychosis: onset within the first 2 weeks after delivery of severe insomnia, confusion and disorientation, rapidly shifting mood, hallucinations, and delusions about the infant (here, that the baby is an impostor). It affects about 1 to 2 per 1,000 deliveries and is strongly linked to bipolar disorder; it is often the first manic or mixed episode, and a family history of bipolar disorder, as in her mother, is a major risk factor. Normal vital signs, blood pressure, and laboratory results make eclampsia, infection, thyroid disease, and intoxication unlikely.

Postpartum psychosis is a psychiatric emergency because of the risk of suicide and infanticide. The next step is immediate inpatient psychiatric admission, involuntarily if she refuses, and she should not be left alone with the infant. Treatment is an antipsychotic plus lithium or another mood stabilizer, with a benzodiazepine for agitation or insomnia; ECT is used for severe or refractory illness.

A. A hypnotic alone ignores psychosis with possible danger to the infant. B. Postpartum blues cause tearfulness and lability with intact function and reality testing; hallucinations, delusions, and confusion are never blues. C. Sertraline and psychotherapy treat postpartum depression; an antidepressant alone may worsen a bipolar mixed or manic episode and leaves her unsafe. D. Delaying evaluation by days is unsafe because postpartum psychosis escalates rapidly.

This patient has delusional parasitosis, which in the absence of another cause is classified as delusional disorder, somatic type. The key features are a fixed, false belief of skin infestation that persists despite negative scrapings and repeated failed antiparasitic treatment, the specimen sign (also called the matchbox or baggie sign) in which the patient brings debris she believes contains the organisms, and secondary excoriations from attempts to remove them. Her function outside the delusion is preserved, as is typical of delusional disorder, and the workup has excluded the main secondary causes: stimulant use, thyroid disease, B12 deficiency, renal or hepatic disease, and true infestation.

The diagnosis guides treatment. An antipsychotic such as risperidone or olanzapine is first line, introduced within a trusting relationship by focusing on her distress and symptoms rather than arguing about the existence of the insects. Further courses of permethrin or ivermectin only reinforce the belief.

A. Cocaine-induced formication causes the sensation of bugs under the skin, but it requires stimulant exposure, and her history and urine drug screen are negative. B. Excoriation disorder is recurrent picking driven by an urge or tension, without a delusional explanation; DSM-5 excludes it when picking results from a delusion of infestation. D. Obsessive-compulsive disorder can feature poor or absent insight, but its obsessions are intrusive, unwanted thoughts that drive rituals; here the belief is a single fixed delusion of infestation with no obsessions or compulsions. E. Scabies is excluded by negative scrapings, absence of burrows, no response to two appropriate treatments, and an unaffected close contact.

This man shows malingering: the intentional production or gross exaggeration of symptoms motivated by external incentives, here financial compensation from a lawsuit and disability documentation to avoid work. Clues include a medicolegal context, a marked discrepancy between reported disability and objective findings (normal neurologic examination and imaging after a minor collision), nonphysiologic responses such as extreme pain to light touch, and inconsistency between behavior when observed by the examiner and behavior when unobserved. Malingering is a behavior rather than a mental disorder. Symptoms often stop once the goal is achieved. The physician should document objective findings carefully, avoid accusatory language, decline to certify disability that the examination does not support, and screen for coexisting psychiatric or substance use conditions.

A. Factitious disorder also involves intentional feigning, but the motive is internal, to assume the sick role, with no external reward; this patient's goal is clearly money and time off work. C. Conversion disorder causes involuntary neurologic symptoms incompatible with anatomy, usually after a stressor; the patient is not consciously producing them, and pain alone is not a functional neurologic deficit. D. Somatic symptom disorder involves genuine, unintentional distress and excessive thoughts and behaviors about symptoms, typically for longer than 6 months, without deliberate deception. E. Illness anxiety disorder is fear of having a serious disease with minimal symptoms; this man does not fear an illness and is seeking documentation, not diagnosis.

Every patient starting a second-generation antipsychotic needs metabolic monitoring, because these drugs cause weight gain, insulin resistance, type 2 diabetes, and dyslipidemia, and people with serious mental illness die prematurely of cardiovascular disease. Quetiapine carries intermediate metabolic risk, and this patient also has a family history of diabetes. The standard schedule obtains weight (BMI), waist circumference, blood pressure, fasting glucose or A1c, and a lipid panel at baseline; weight is rechecked monthly for 3 months and then quarterly, and blood pressure, glucose or A1c, and lipids are rechecked at about 12 weeks. Glucose or A1c is then checked yearly; lipids are rechecked yearly in the APA guideline (the 2004 consensus allowed every 5 years if normal). At this 12-week visit, she is therefore due for glucose or A1c and lipid testing, and abnormal results would prompt lifestyle intervention, a switch to a weight-sparing agent, or metformin.

B. A routine ECG is not part of metabolic monitoring; it is indicated before QT-prolonging agents in patients with cardiac disease, electrolyte abnormalities, or other QT-prolonging drugs, none of which apply. C. Prolactin is measured when symptoms of hyperprolactinemia (galactorrhea, menstrual disturbance, sexual dysfunction) develop, particularly with risperidone or paliperidone; quetiapine has little prolactin effect and she is asymptomatic. D. Routine blood counts are required for clozapine (ANC monitoring), not for quetiapine. E. TSH is monitored with lithium therapy, which causes hypothyroidism, not with quetiapine.

This patient has taken alprazolam three times daily for 8 years, which reliably produces physical dependence, and her supply was abruptly cut off on admission because the drug was missing from her medication list. Alprazolam is short acting, so withdrawal begins early, within 1 to 2 days, and is intense. The features (anxiety, tremor, diaphoresis, tachycardia, hypertension, perceptual disturbances such as visual hallucinations, and a withdrawal seizure) mirror alcohol withdrawal because both involve sudden loss of GABA-A enhancement. Benzodiazepine withdrawal seizures can be fatal. Treatment is to restore a benzodiazepine (often a long-acting one such as diazepam or clonazepam at an equivalent dose) and later taper slowly over weeks to months. The case also illustrates why medication reconciliation should include prescription monitoring data.

A. Alcohol withdrawal delirium produces an identical syndrome but requires heavy, sustained alcohol use; she drinks only on holidays. B. Fat embolism syndrome after orthopedic surgery causes confusion with hypoxemia and petechial rash, typically within 1 to 3 days; her oxygen saturation is normal, there are no petechiae, and it does not explain tremor and hallucinations with autonomic hyperactivity. D. Opioid toxicity causes sedation, miosis, and respiratory depression, the opposite of her agitated, hyperadrenergic state with 5-mm pupils. E. Serotonin syndrome requires serotonergic drugs and is distinguished by hyperreflexia and clonus; she takes none, and her reflexes are normal without clonus.

When a person with dementia has an abrupt change in behavior, the first assumption should be discomfort or a medical problem that the patient cannot describe. This woman became agitated and food-refusing within days of starting an opioid, has a distended, tender lower abdomen with hypoactive bowel sounds, and is passing small amounts of liquid stool. That combination is fecal impaction with overflow incontinence: liquid stool leaks around a hard fecal mass, and staff often mistake it for diarrhea. The next step is a digital rectal examination, followed by disimpaction and a bowel regimen with a scheduled laxative while the opioid continues, and agitation often resolves once the impaction is relieved.

The recommended approach to behavioral and psychological symptoms of dementia is to describe the behavior, search for triggers (pain, constipation, urinary retention, infection, dehydration, sensory loss, and new drugs such as opioids, anticholinergics, and benzodiazepines), then use nonpharmacologic measures, reserving medications for danger. Giving an antipsychotic here would add mortality and stroke risk while missing the cause.

A. Progression of Alzheimer disease is gradual over months to years and would not explain abdominal distension or tenderness after a new opioid. C. A urinary tract infection is unlikely with a negative urinalysis, and the low postvoid volume excludes urinary retention. D. C. difficile colitis causes frequent watery diarrhea, often with fever and leukocytosis, typically after antibiotics; she has no fever and no recent antibiotic exposure, and her small-volume leakage with hypoactive bowel sounds fits overflow around an impaction. E. A primary late-life psychosis is a diagnosis of exclusion and would not cause abdominal findings.

The key question in a patient with both psychosis and mood episodes is whether psychosis ever stands alone. This woman has had recurrent manic and depressive episodes accompanied by hallucinations and a bizarre delusion, and her mood episodes account for most of the total duration of her illness. Critically, for the past 5 weeks her mood has been normal while the hallucinations and delusion persist. At least 2 weeks of delusions or hallucinations without prominent mood symptoms, together with major mood episodes concurrent with schizophrenia-criteria psychosis for the majority of the illness, defines schizoaffective disorder. Because manic episodes are part of the presentation, the subtype is bipolar type. Treatment usually combines an antipsychotic with a mood stabilizer.

A. Bipolar I disorder with psychotic features would apply if psychosis occurred only during mood episodes; here psychosis has persisted for weeks after euthymia returned.

B. Schizophrenia is diagnosed when mood episodes are absent or present for only a minority of the total duration of active and residual illness; her prominent, recurrent mood episodes make schizophrenia less fitting.

D. Delusional disorder involves delusions without prominent hallucinations or mood episodes, with preserved function; she has hallucinations and full manic and depressive episodes.

E. Schizophreniform disorder describes schizophrenia-type symptoms lasting 1 to 6 months without the prominent mood episodes she has had over 3 years.