A 26-year-old woman is evaluated in the clinic due to absence of her last 3 menstrual periods.  The patient has also developed bilateral milky nipple discharge.  Menarche was at age 13.  Until now, she has had regular menses, lasting 4-5 days, every 28 days.  The patient says she takes acetaminophen for occasional headaches and a medication that “stops the voices” in her head.  BMI is 29 kg/m².  Pelvic examination is unremarkable.  Urine β-hCG testing is negative.  Interruption of which of the following central nervous system pathways is the most likely cause of this patient’s presenting symptoms?

A 60-year-old woman comes to the office due to uncontrollable movements that have worsened.  Medical history is significant for hypertension, hyperlipidemia, osteoarthritis, and schizophrenia, and she has been on a stable medication regimen for years.  Throughout the interview, she exhibits facial grimacing, lip smacking, and twisting movements of her hands and feet.  The patient has lived in a group home for many years and worries that her housemates are avoiding her because her symptoms make her look “strange.”  On mental status examination, the patient makes poor eye contact and is generally distrustful but has no specific delusions or hallucinations.  Which of the following is the most likely diagnosis?

A 28-year-old man is brought to the emergency department by his roommate, who is concerned about his change in behavior over the past 2 weeks.  The roommate describes the patient as “a regular guy who is usually very responsible.”  Last week, the patient abruptly quit his job as a computer programmer and started placing large bets on an online gambling site because he was “sure to make millions.”  The roommate says that the patient has been staying up most nights scribbling notes for his autobiography on small scraps of paper.  The patient says, “My new mission is to spread understanding.”  He denies any alcohol or drug use, which his roommate affirms.  This patient is most likely to exhibit which of the following additional findings?

A 61-year old woman comes to the office due to insomnia.  She has had difficulty falling asleep since her divorce was finalized 2 months ago and she relocated to a new state to be closer to her daughter and grandchildren.  The patient’s sleep is restless and she is frequently awakened by household noises.  During this time, she has also felt anxious and tense.  The patient is overwhelmed by financial worries and the responsibilities of living on her own.  Although previously outgoing, she now avoids opportunities to meet new people and socializes only with her daughter.  The patient has no psychiatric history but does have a history of hypothyroidism treated with levothyroxine.  Physical examination is unremarkable.  TSH is 1.6 µU/mL.  Which of the following is the most likely diagnosis?

A 35-year-old woman comes to the office due to worsening fatigue and tension headaches over the past year.  She describes always feeling “on edge” and lies awake at night worrying about various issues such as whether she is good at her job, whether her grown children like her, if she will get cancer one day, and whether her house will be broken into.  During the day she feels tired and her shoulders and neck ache; she has difficulty concentrating on her work and has become increasingly concerned about losing her job.  The patient has no medical or psychiatric history.  Physical examination and routine laboratory studies, including thyroid function tests, are normal.  The patient’s anxiety has never been treated, but she once took a tablet of alprazolam offered by a friend.  This lowered her anxiety, but the effect did not last long.  The patient drinks a glass of wine on rare social occasions and does not use illicit drugs.  Which of the following is the most appropriate pharmacotherapy for this patient?

A 19-year-old man comes to the office for evaluation of a hand injury.  He says, “I was just minding my own business at work when this dog bit me.”  The patient recently started operating a dog-fighting club and adds that his “entrepreneurial skills” have made him “richer than a doctor.”  He has been fired from multiple jobs, most recently while working as a car salesman, due to getting into arguments with coworkers and being repeatedly late to shifts.  The patient says, “I was only late a few times.  Haven’t you ever been late before, doc?”  During middle school, he was recurrently truant and spent time at a juvenile detention center for tampering with his teacher’s car brakes after failing a class.  Which of the following is the most likely diagnosis?

A 30-year-old man comes to the office due to depression.  He describes a 4-week history of severely depressed mood, loss of motivation, loss of interest, and sleeping 12 hours a day.  The patient has difficulty concentrating and worries that it is interfering with his work.  He is pessimistic about the future but has no suicidal thoughts.  The patient had a previous depressive episode in his 20s that responded rapidly to sertraline.  He felt “really good and energetic” after a few days of treatment but discontinued the antidepressant a week later as he did not feel that he needed it.  He drinks 1 or 2 beers on social occasions.  Physical examination is normal.  Which of the following would be most important to assess prior to initiating pharmacologic treatment for this patient?

A 13-year-old boy is brought to the office due to anxiety and behavioral problems at school.  Although he has good grades, he frequently feels overwhelmed at school and his mother worries that he is socially awkward and has no friends.  The patient often appears anxious and uncomfortable in new social situations.  He insists on sitting in the same row and seat in every class and has had several inappropriate outbursts when told by teachers that this was not possible.  After school, the patient prefers to spend time at home.  His mother observes that he is obsessed with dates and comparing solar and lunar calendars and can discuss this for hours, but has difficulty shifting to other topics of conversation.  The patient was born at full term, and developmental milestones were within normal range.  Physical examination is unremarkable.  Which of the following is the most likely explanation of this patient’s behavior?

A 17-year-old girl is brought to the office by her parents due to recurrent episodes where “she seems to be lost in her own world.”  The parents say that the episodes began about 2 years ago, but seem to be occurring more frequently since a difficult breakup with her boyfriend several months ago.  The patient acknowledges that she seems to “space out” easily.  She says, “I often feel numb, like I’m in a fog or a dream.  Sometimes, I feel as if I’m not myself, as if things are happening to someone else.”  The patient uses nonsteroidal anti-inflammatory drugs for menstrual cramps.  She has no other medical conditions.  She smokes cigarettes but does not use alcohol or illicit drugs.  Physical and neurologic examinations are normal.  On mental status examination, the patient is cooperative with a mildly anxious mood and flat affect.  Which of the following is the most likely diagnosis?

A 32-year-old woman comes to the emergency department requesting medication for severe back pain.  She has tried multiple over-the-counter agents and says that nothing has relieved her pain except oxycodone.  The patient was seen in a pain clinic a year ago but cannot recall the name of the physician and says that her prescription has run out.  Medical history includes a motor vehicle collision 10 years earlier and obesity.  Temperature is 37.1 C (98.8 F), blood pressure is 130/80 mm Hg, pulse is 76/min, and respirations are 16/min.  Physical examination shows no abnormalities.  A recent MRI was normal.  The patient says that her pain level is 10 on a scale of 0-10 and becomes frustrated when the physician suggests nonprescription pain medication.  Which of the following is the most appropriate next step by the physician?

A 21-year-old woman, gravida 1 para 0, comes to the office for a prenatal visit at 16 weeks gestation.  The patient, who has not gained weight since her last visit 4 weeks ago, has occasional nausea with vomiting twice a week.  She has little appetite, which she attributes to mild indigestion, and her food consumption has decreased.  However, the patient craves ice and has been consuming it throughout the day for the last few months.  Medications include daily prenatal vitamins.  The patient was prescribed twice-daily iron for anemia but does not take it because it causes constipation.  She has no diarrhea, dysuria, chills, or fever.  The patient does not use tobacco.  The uterine fundus is consistent with a 16-week pregnancy.  Fetal heart tone is 140-149/min.  The patient’s vital signs are within normal limits.  Which of the following is the most likely diagnosis?

A 16-year-old girl is brought to the office by her mother due to nonspecific stomachaches and pains.  She has no other medical history.  The patient has missed more than 10 days of school due to the symptoms since the academic year started 6 months ago.  The mother says that her daughter has always been anxious with a “sensitive stomach,” but the symptoms have worsened since the patient’s best friend moved away a month ago.  She has a few other friends but prefers to stay home and does not participate in after-school activities.  The mother says, “She worried for weeks about going to a party.  On the night of the party she had an anxiety attack and started hyperventilating.  She ended up not going to the party at all.”  The patient says she is “just very shy” and is afraid of being embarrassed or “looking stupid” around others.  Physical examination shows no abnormalities.  During the interview, the patient makes little eye contact and gives brief answers to questions.  Which of the following is the most likely diagnosis?

A 42-year-old man comes to the office for a checkup.  He has no medical symptoms but says, “I’m just feeling stressed and not like myself.”  The patient is going through a contentious divorce.  He is outraged that his wife is pursuing full custody of their children and says, “I can’t believe she is doing this to me.”  His job as a legal researcher had been a welcome distraction from his upsetting personal life until yesterday when he was called to his supervisor’s office for yelling at the receptionist when the copy machine ran out of ink.  Which of the following is the best explanation for this patient’s behavior toward the receptionist?

A 14-year-old boy is brought to the office by his parents, who are worried about his reaction to their recent decision to divorce.  Despite their efforts to be supportive and engage him, he has not expressed any feelings directly about the divorce.  When the patient is evaluated alone, he shares that he feels his parents are angry with him, although he cannot think of any instances when they expressed any anger toward him.  On examination, the patient appears sullen and reports his mood is “fine.”  This patient is most likely using which of the following defense mechanisms?

A 40-year-old woman comes to the emergency department fearing she is having a heart attack.  While clutching her chest and breathing heavily, she says, “I feel like I’m dying.”  Temperature is 37.2 C (99 F), blood pressure is 125/86 mm Hg, pulse is 110/min and regular, and respirations are 18/min.  The patient’s pulse oximetry shows 98% on room air.  Laboratory evaluation and ECG show no abnormalities.  The pain resolves within 10 minutes without treatment, and the patient reports, “I was taking the bus home from work when my chest started feeling really tight.  I’m lucky my friend was there and able to help me get to the hospital.  What if she’s not there next time?”  She describes experiencing similar episodes at random places and times that are characterized by a pounding heart, trembling, dizziness, and sweating.  She drinks alcohol socially and does not use any medications.  This patient is most likely to develop which of the following disorders as a result of her current condition?

A mouse model of focal dystonia due to mutations in DYT-TOR1A is being studied.  Humans with this mutation have variable expressivity of diverse forms of dystonia, including cervical dystonia (ie, torticollis), writer’s cramp, and lower limb dystonias.  Histologic analysis of an affected muscle in one of the experimental mice is most likely to show which of the following?

A 6-year-old boy is brought to the office by his mother due to frequent nighttime awakenings.  Over the past several months, the patient has had weekly episodes of waking up screaming at night.  His mother says, “He seems fine when we’re reading his bedtime story, but 1-2 hours after falling asleep, he wakes up shrieking.  He looks scared, hyperventilates, and cries.  When I try to hug him, he pushes me away and eventually falls back asleep.”  The mother is concerned that the patient is watching horror movies with his older brother; however, she mentions that the next morning he does not remember his dreams or having awakened.  Which of the following is the most likely diagnosis?

A 40-year-old woman comes to the office due to lesions on her left arm.  She developed small, red sores a few weeks ago, and over the past few days, they have increased in number.  The patient is very concerned that they will cause an infection because she has had similar lesions on her extremities many times in the past; wound cultures have consistently grown Escherichia coli.  Most recently, she developed cellulitis 8 months ago and required intravenous antibiotics.  The patient says, “I don’t know why my skin keeps getting infected.  I’ve been to so many doctors, and none of them can tell me what’s going on.”  She lives alone and works as a traveling nurse.  Medical history is otherwise noncontributory.  Which of the following is most characteristic of this patient’s condition?

A 48-year-old man begins psychotherapy due to depression and escalating conflicts with his boss.  He makes progress in the therapy sessions and reports feeling less depressed.  The patient has also gained insight into how his father was rarely available to him while growing up and recently told his father, “I am angry that you were never there for me.”  The following week, the psychiatrist unexpectedly cancels a session to attend to an emergency.  At the next appointment, the patient says, “I feel as if you are not interested in listening to me, like I am not your priority.”  Which of the following is the most likely explanation of this patient’s attitude toward his psychiatrist?

A 62-year-old woman comes to the office for follow-up of worsening hypertension.  The patient admits to not taking her antihypertension medication as prescribed.  She says she feels fine and adds, “I always listen to my bodily rhythms when deciding whether to take medication on a particular day.”  The patient explains that her crystal jewelry has healing powers, and she maintains an online forum about the health benefits of crystals.  The patient does not trust most people and believes that she can predict the weather based on the number of birds in her yard.  She lives alone, has few friends, and is unemployed.  On examination, the patient makes limited eye contact and appears mildly anxious.  She has no auditory hallucinations, and no specific delusions are elicited.  Which of the following is the most likely explanation for this clinical presentation?

An 18-year-old man is brought to the clinic by his mother due to increasingly bizarre behavior over the past 2 months.  The patient is in his first semester at an out-of-state college and has had difficulty adjusting to being away from home.  For the past few weeks, he has not been attending classes, and he no longer socializes with friends.  The patient spends most of his time alone in his dorm room and eats very little because he believes the cafeteria food is poisoned.  He has no significant medical or psychiatric history and does not use alcohol or illicit drugs.  Physical examination is unremarkable.  On mental status examination, he appears disheveled with unwashed hair, makes poor eye contact, and shouts “leave me alone” in response to unseen people.  Which of the following is the most likely diagnosis in this patient?

A 24-year-old man comes to the office for treatment of opioid use disorder.  The patient has a 6-year history of heroin use, which he says has cost him most of his savings.  His boss has spoken to him about his erratic moods and inconsistent work performance, and he is now in danger of losing his job.  The patient asks for help, saying, “I have tried so hard to do this on my own.  My parents have spent a lot of money on counseling.  It helps for a while, but then I go back to using.  They are fed up and refuse to see me anymore.  I don’t want to use, but the craving is so strong.”  The physician refers the patient to an opioid treatment program where he is started on maintenance therapy with methadone.  During the next followup appointment, he reports a marked reduction in his cravings.  Which of the following properties of the administered drug is most likely responsible for the improvement in this patient’s condition?

A 5-year-old boy is brought to the office by his parents for a well-child visit.  His mother says, “My son is doing very well.  He is able to read at a first-grade level and knows his name and address.  He loves to sing, dance, and play house with his older sisters.  Everything seems fine with him; we just want to make sure his vaccinations are up to date before our family trip overseas.”  The physician administers the appropriate vaccinations.  Just before leaving, the father says, “I think you should know that my son is playing with his sister’s dolls and doesn’t seem to like cars or trucks like most other boys.  Is that normal?”  Which of the following is the most appropriate response to the father’s concerns?

A 20-year-old college student comes to the office due to fatigue and decreased exercise tolerance.  She says, “I used to run 5 miles every day, but for the past month I get out of breath after running 3 miles.  I need to keep running so I don’t get any fatter than I already am.”  The patient also reports difficulty concentrating in class, depressed mood, constipation, and abdominal bloating.  Her appetite is normal, but she admits to occasionally forcing herself to vomit to prevent weight gain.  Physical examination is significant for dry skin, painless bilateral parotid swelling, pharyngeal erythema, and hypoactive bowel sounds.  Temperature is 36.2 C (97.2 F), blood pressure is 100/60 mm Hg, pulse is 62/min, and respirations are 16/min.  BMI is 17.5 kg/m².  Which of the following is the most likely diagnosis?

A 63-year-old woman with a history of metastatic breast cancer comes to the office due to depressed mood.  Over the past month, the patient has become increasingly sad and frequently cries when thinking about her poor prognosis and dying.  She has lost 4.5 kg (10 lb) over the past month.  Her energy level is low, and she has difficulty falling asleep and frequent nighttime awakenings.  The patient has become very withdrawn, doesn’t answer the phone, and no longer looks forward to family visits.  She feels bad about not wanting to be around her grandchildren.  On mental status examination, the patient is alert and oriented with depressed mood and affect.  She has no suicidal ideation.  Which of the following symptoms is most indicative of major depressive disorder in this patient?

A 25-year-old man is brought to the emergency department by ambulance after being found sitting in the street drinking his own urine.  The patient’s mother says that a year ago he expressed the belief that he was being watched by an unidentified government agency and subsequently broke up with his girlfriend, quit his job, and disconnected his phone.  The patient’s mother has noticed that he no longer seems to care about activities that used to interest him, and last month she found out that he had moved into the family garden shed with his dog.  On examination, the patient is malodorous, disheveled, and laughs for no apparent reason.  He later becomes angry and refuses to sit in a chair for the interview.  The patient switches among unrelated topics and when asked where he lives says, “in the holy buffet of diplomacy.”  Temperature is 36.7 C (98 F), blood pressure is 122/79 mm Hg, and pulse is 80/min.  Physical examination and laboratory evaluation, including urine toxicology, are unremarkable.  Which of the following is the most likely diagnosis in this patient?

A 52-year-old man diagnosed with advanced pancreatic cancer comes to the oncologist for follow-up.  His cancer is unresectable, and he has been receiving palliative treatment for the past 3 months.  The patient has had multiple previous discussions about his prognosis.  He has lost 22.6 kg (50 lb) and now feels too weak to play with his children.  During the visit, he says, “I am a survivor and know I can beat this.  I’m going to do whatever I can to be around for my kids.”  Which of the following is the most appropriate response to this patient at this time?

A 42-year-old man is brought to the hospital after a motor vehicle collision.  The patient was driving while intoxicated with alcohol and collided with another car.  Evaluation reveals a left tibia and fibula fracture but no other major injuries.  He reports no prior medical conditions.  The patient is hospitalized and operative repair of the fracture is performed.  On the third day in the hospital, he becomes agitated and demands to leave.  Temperature is 37.2 C (99 F), blood pressure is 162/94 mm Hg, and pulse is 125/min.  On physical examination, the patient is diaphoretic, tremulous, and disoriented.  There are mild hand tremors but no other neurologic abnormalities.  Increased activity of which of the following central nervous system receptors is the most likely cause of this patient’s condition?

A 60-year-old man comes to the office to discuss sexual symptoms.  Eight weeks ago, the patient was admitted to the hospital with a non–ST-elevation myocardial infarction, and a drug-eluting stent was successfully placed in the culprit coronary artery.  The patient now has no cardiovascular symptoms, including when climbing stairs or taking long walks.  Since discharge, he has had difficulty maintaining an erection and delayed ejaculation during sexual intercourse, but he has normal libido and regular nocturnal erections.  Medications include metoprolol, rosuvastatin, aspirin, and ticagrelor.  Vital signs and physical examination are normal.  Which of the following is the most likely cause of this patient’s sexual dysfunction?

A 5-year-old boy is brought to the office by his parents due to bed-wetting.  The patient has stayed dry during the day since age 3 but has continued to wet the bed 4 or 5 nights a week.  He urinates approximately 5 times during the day; the urinary stream is continuous and strong.  Bowel movements occur daily and are soft.  The patient is otherwise healthy and takes no daily medications.  Height and weight are tracking along the 75th percentile.  Vital signs and examination are normal.  Urinalysis is unremarkable.  This patient’s bed-wetting is most likely caused by which of the following?

A 45-year-old man with a history of chronic alcohol use disorder is brought to the emergency room due to altered mental status.  The patient appears malnourished.  He is given thiamine, folic acid, a multivitamin, and dextrose-containing intravenous fluids.  However, the patient develops marked muscle weakness a few hours later.  Laboratory studies reveal a serum phosphate concentration of 0.5 mg/dL (normal: 2.5-4.5).  Which of the following is the most likely cause of this patient’s low serum phosphate level?

A 26-year-old man is brought to the emergency department by police after assaulting customers in a restaurant.  He explains that he meant no harm and was just trying to talk to people and touch them to “heal their pain.”  The patient has been up all night for the past 10 days devising a global strategy to end world hunger and has written a hundred-page manifesto documenting his ideas.  Over this same period, he began hearing a voice telling him that he is “God’s true son” and will need to sacrifice his life.  The patient has no psychiatric or medical history.  He drinks alcohol socially but does not use illicit drugs.  Physical examination is normal.  On mental status examination, the patient paces continuously.  His mood is very irritable, and his speech is loud, rapid, and difficult to interrupt.  Which of the following is the most likely diagnosis in this patient?

A 48-year-old man comes to the office with his wife for follow-up of major depressive disorder.  The patient has been taking sertraline for 2 years, and due to a recurrence of depression, he started bupropion and weekly cognitive behavioral therapy 3 weeks ago.  Since then, his energy level has improved, and he is working on communicating more with his wife about his emotions.  The patient has no suicidal ideation and is hopeful that he will feel better with continued treatment.  A week later, his wife calls the office and states that her husband died by suicide a few days ago.  She is tearful on the phone and says, “I thought that he was doing better.  I don’t understand how this happened.”  Which of the following is the most appropriate response?

A 49-year-old man comes to the office due to dysuria and hematuria.  Vital signs are within normal limits and physical examination is unremarkable; urinalysis shows gross hematuria but is otherwise normal.  The physician discusses potential causes and the need for a cystoscopy.  The patient is told what to expect during the procedure and is given written information and a referral list with instructions on how to schedule an appointment with a urologist.  He anxiously glances over the papers, saying he will make an appointment soon.  Office staff had informed the physician that the patient was unable to follow the directions on the sign-in sheet and declined to fill out paperwork.  Which of the following physician responses is the most appropriate at this time?

A 72-year-old, previously healthy man is brought to the office by his wife due to unusual movements and behavior during sleep that have occurred with increasing frequency over the past 3 months.  She says, “Lately, he’s been waking me up in the middle of the night, moaning and thrashing around like he’s having a bad dream.  Sometimes, he becomes so violent in his sleep that he’ll kick and punch me.  I can easily wake him up, but he’s often confused for a few seconds.  Then he usually describes a dream in which he was defending himself from an attack.”  Physical examination is unremarkable.  Neurodegeneration due to accumulation of which of the following is the most likely etiology of this patient’s condition?

A 55-year-old, previously healthy man is brought to the office by his wife after being forced into early retirement due to poor work performance.  The patient was a financial planner but began missing important deadlines and mismanaging his client’s accounts 6 months ago.  He became more irritable during this time and started to curse at and insult his coworkers when they expressed concern about his performance.  The patient has also become verbally abusive toward his wife but appears indifferent to the hurt he causes.  She has had to take over the finances and grocery shopping.  She adds, “My husband has developed quite the sweet tooth.  He eats almost two boxes of cookies a day now.”  Physical examination is unremarkable.  This patient is most likely to have which of the following neuropathologic findings?