# Free 120 Step 2 CK: Item Map and Explanations

> What is the Step 2 CK Free 120?

The Free 120 is the set of USMLE Step 2 CK sample test questions published free on usmle.org. The PDF linked there still lays the set out as 120 items in three 40-item blocks, with an answer key. A separate interactive version reflects the shorter block format the exam moved to in May 2026.

## Where to get it

- Official sample questions page: https://www.usmle.org/exam-resources/step-2-ck-materials/step-2-ck-sample-test-questions
- Official PDF: https://www.usmle.org/sites/default/files/2021-10/Step2_CK_Sample_Questions.pdf
- Official interactive testing experience: https://www.starttest.com/custom/usmle/?stpf2

Built from the Step 2 CK sample-questions booklet linked from the official Step 2 CK sample-questions page, read on 2026-09-05. The cover is marked "updated July 2023"; usmle.org re-uploaded the file on 2025-08-25 (its Last-Modified header), so treat the cover date as the edition and re-check the item numbering if the file changes again. StepGenie does not host or mirror the booklet, and does not reproduce its vignettes, answer options or images.

## How the booklet is built

- The booklet carries 120 numbered items in three blocks of 40 and prints the answer key at the end.
- Step 2 CK itself moved to sixteen 30-minute blocks of up to 20 items on May 7, 2026, so the booklet's three-block layout no longer matches test day.
- The interactive testing experience linked from the same official page is the version that reflects the current format.
- Item numbers on this page follow the PDF usmle.org currently links. If a new booklet is posted, the numbering will change.

## Item map

One row per numbered item in the official booklet. block = the booklet block the item sits in. system and topic are our own editorial tags. paraphrase is an original one-line summary of what the item asks, written to be substantively different from the booklet text. No vignette text, answer options or answer key is stored here.

### Block 1

| # | System | Topic | What the item asks | Explanation |
|---|---|---|---|---|
| 1 | Behavioral Health | Panic disorder with agoraphobia | College student with recurrent panic attacks now avoiding public places and dates; most likely diagnosis. | published |
| 2 | Cardiovascular / Nervous System | Paradoxical embolism workup | Young man with MCA stroke while lifting weights plus leg swelling; normal carotids; next diagnostic step. | published |
| 3 | Respiratory / Pharmacology | Amiodarone pulmonary toxicity | Man on multiple cardiac drugs with progressive dyspnea, dry cough, bilateral fine crackles; culprit medication. | published |
| 4 | Musculoskeletal (Pediatrics) | Osteogenesis imperfecta surveillance | Toddler with recurrent fractures, blue sclerae, maternal fracture history; which regular screening is indicated. | in review |
| 5 | Social Sciences / Ethics | Surrogate decision-maker hierarchy | Incapacitated woman without POA, cared for by long-term boyfriend and neighbor; who decides. | in review |
| 6 | Cardiovascular (Pediatrics) | Postoperative cardiac tamponade | Infant days after VSD repair develops fever, poor perfusion, oliguria; rhythm strip and arterial tracing shown. | in review |
| 7 | Renal (Pediatrics) | Nephrotic syndrome | Six-year-old with periorbital and leg edema and heavy proteinuria (chart format); which lab is decreased. | in review |
| 8 | Respiratory (Pediatrics) | Persistent asthma step-up | Child with weekly nocturnal cough and exercise limitation on PRN albuterol only; next management step. | in review |
| 9 | Cardiovascular / Preventive | Lipid screening | 30-year-old smoker with paternal early MI and overweight establishing care; appropriate screening study. | in review |
| 10 | Nervous System / Nutrition | Vitamin B12 deficiency neuropathy | Elderly woman with decades of calcium carbonate and wine, loss of vibration/proprioception and reflexes; prevention. | in review |
| 11 | Gastrointestinal / Oncology | Oral leukoplakia | Chewing-tobacco user with a persistent white buccal patch; next step beyond cessation counseling. | in review |
| 12 | Cardiovascular | Alcoholic dilated cardiomyopathy | Heavy drinker with progressive heart failure, S3, crackles, edema; expected echocardiographic finding. | in review |
| 13 | Nervous System | Parkinson postural instability | Parkinson patient with retropulsion and frequent falls on levodopa; best intervention to reduce falls. | in review |
| 14 | Behavioral Health (Pediatrics) | Specific learning disorder | Adopted 6-year-old with average IQ, appropriate daily skills, unable to read in any language; diagnosis. | in review |
| 15 | Immune / Emergency | Anaphylaxis | Teen on amoxicillin with urticaria, respiratory distress, hypotension; next step. | in review |
| 16 | Infectious / Patient Safety | C. difficile infection control | Post-cholecystectomy patient recently treated for C. difficile still has loose stools; precaution for clinician. | in review |
| 17 | Biostatistics / Evidence-based medicine | Interpreting confidence intervals | Using a buprenorphine-vs-methadone abstract, what to tell a patient about relative efficacy at medium/high doses. | in review |
| 18 | Biostatistics / Evidence-based medicine | Limitations of systematic reviews | Which design feature of the maintenance-therapy meta-analysis most limits confidence in conclusions. | in review |
| 19 | Biostatistics / Evidence-based medicine | Publication bias | Which factor is most likely to bias the results of the systematic review. | in review |
| 20 | Social Sciences / Ethics | Brain death and organ donation | Man with ruptured aneurysm meets brain-death criteria; wife says he wished to donate; next step. | in review |
| 21 | Reproductive / Obstetrics | Intrapartum fetal monitoring | Laboring woman progressing well after amniotomy; fetal heart tracing shown; next step. | in review |
| 22 | Immune | Common variable immunodeficiency | Woman with recurrent sinusitis and pneumonias and low IgA, IgG, IgM; best way to prevent recurrence. | in review |
| 23 | Gastrointestinal / Infectious | Chronic hepatitis B complications | Man from China with fatigue, elevated transaminases, HBsAg positive, anti-HBc IgG; untreated outcome. | in review |
| 24 | Blood & Lymphoreticular (Pediatrics) | Hemophilia A hemarthrosis | Boy with hemophilia A and a warm swollen knee; most appropriate therapy. | in review |
| 25 | Special Senses | Macular degeneration | Elderly man with metamorphopsia (wavy lines) and reduced acuity, clear lens, normal red reflex; diagnosis. | in review |
| 26 | Skin / Toxicology | Brown recluse spider bite | Man bitten by spider in southeastern US with painful red lesion (photo); expected finding within 24 hours. | in review |
| 27 | Cardiovascular / Preventive | Elevated blood pressure lifestyle management | Obese man with repeated BP around 138/87; besides weight loss, best step to prevent cardiovascular morbidity. | in review |
| 28 | Endocrine | New severe hyperglycemia in a thin adult | Thin 39-year-old with weight loss, polyuria, glucose 578, A1c 10.7%; next step beyond diet. | in review |
| 29 | Renal / Nervous System (Pediatrics) | Symptomatic hyponatremia | Child with head injury seizes with sodium 122; next step. | in review |
| 30 | Infectious | Cat-scratch disease | Man with cats and a tender axillary plus epitrochlear lymph node; most likely diagnosis. | in review |
| 31 | Behavioral Health (Pediatrics) | Disclosing adoption | Parents of adopted 2-year-old ask when to tell her about adoption; best advice. | in review |
| 32 | Patient Safety / Quality Improvement | Quality improvement first steps | ICU team wants to reduce central line days and infections; most appropriate next step. | in review |
| 33 | Gastrointestinal | Peptic ulcer / dyspepsia diagnosis | Teen girl with months of postprandial epigastric pain and normal exam; test most likely to confirm diagnosis. | in review |
| 34 | Respiratory / Toxicology | Irritant-induced bronchospasm | Man coughing with diffuse wheezes after inhaling cleaning-agent fumes, stable gas exchange; initial management. | in review |
| 35 | Social Sciences / Ethics | Medical futility | Man with carcinomatosis and recurrent obstruction requests laparotomy previously deemed non-beneficial; next step. | in review |
| 36 | Endocrine | Graves disease / thyrotoxicosis | Woman with weight loss, atrial fibrillation, diffuse goiter with bruit, onycholysis, pretibial myxedema. | in review |
| 37 | Gastrointestinal | Crohn disease and smoking | Young smoker with chronic diarrhea and ileal ulcerations on colonoscopy (chart format); best recommendation. | in review |
| 38 | Cardiovascular / Trauma | Cardiac tamponade after penetrating chest injury | Stab wound medial to left nipple with hypotension and JVD; what FAST results will lead to. | in review |
| 39 | Social Sciences / Ethics / Patient Safety | Missing informed consent in OR | Sedated patient in OR; consent form cannot be found and no site marking; appropriate action. | in review |
| 40 | Reproductive | Male infertility initial evaluation | Man with oligospermia and low-normal testosterone; physician's most appropriate initial action. | in review |

### Block 2

| # | System | Topic | What the item asks | Explanation |
|---|---|---|---|---|
| 41 | Infectious | Acute HIV infection diagnosis | Traveler back from Malaysia with febrile illness, leukopenia, negative monospot; next diagnostic step. | in review |
| 42 | Renal / Toxicology | Rhabdomyolysis | Opioid overdose found down with cold cyanotic leg, CK 50,000, hyperkalemia; greatest risk. | in review |
| 43 | Behavioral Health / Toxicology | Lithium toxicity | Bipolar patient becomes confused and seizes after outdoor exertion in heat; AV block; responsible drug. | in review |
| 44 | Reproductive / Obstetrics | Müllerian anomaly pregnancy risk | Infertile woman with congenital absent kidney and hysterosalpingogram shown; greatest future pregnancy risk. | in review |
| 45 | Cardiovascular / Pharmacology (Pediatrics) | Orthostatic hypotension from clonidine | Teen on several new drugs with light-headedness and orthostatic BP drop (chart format); culprit drug. | in review |
| 46 | Cardiovascular / Preventive | Asymptomatic peripheral arterial disease | Former smoker with absent pedal pulses and femoral bruit but no symptoms; next step. | in review |
| 47 | Patient Safety / Pharmacology | Warfarin drug interaction near miss | Warfarin patient given TMP-SMX develops INR 5.2; what would have prevented the near miss. | in review |
| 48 | Endocrine | Insulin resistance in type 2 diabetes | Type 2 diabetic with rising glucose despite exercise; predict glucose, insulin, receptor responsiveness pattern. | in review |
| 49 | Blood & Lymphoreticular / Pharmacology | Drug-induced neutropenia | Woman on day 6 of TMP-SMX with fever, sore throat, and severe neutropenia; explanation. | in review |
| 50 | Musculoskeletal | Ottawa ankle/knee rules | Man with ankle rolled and stable knee exam, tender distal fibula; decide imaging for knee and ankle. | in review |
| 51 | Endocrine (Pediatrics) | Short stature / delayed puberty evaluation | 13-year-old girl with lifelong short stature, delayed puberty, familial late puberty; next diagnostic step. | in review |
| 52 | Skin | Keloid treatment | Young woman with a growing ear lump after piercing (photo); most appropriate initial treatment. | in review |
| 53 | Respiratory / Trauma | Traumatic hemopneumothorax | Restrained driver with decreased right breath sounds, hypoxemia, chest x-ray shown; next step after analgesia. | in review |
| 54 | Gastrointestinal / Infectious | Giardiasis | Woman with chronic nonbloody diarrhea and weight loss after drinking pond water while camping; stool smear. | in review |
| 55 | Biostatistics / Epidemiology | Absolute risk reduction | SERM vs placebo breast cancer rates per 1000 woman-years; compute absolute risk reduction. | in review |
| 56 | Gastrointestinal | Upper GI bleeding evaluation | Woman with hematemesis, early satiety, tachycardia; after fluids and NG lavage, next step (sequential set). | in review |
| 57 | Gastrointestinal | Endoscopic management of bleeding lesion | Same patient; endoscopic photograph of the bleeding source shown; next management step. | in review |
| 58 | Reproductive / Oncology | Vulvar lesion in elderly woman | Bedbound elderly woman on warfarin with bleeding and a raised fleshy labial lesion; next step. | in review |
| 59 | Musculoskeletal / Nervous System | Lumbar spinal stenosis | Older smoker with back/leg pain on standing relieved by sitting, normal ABI; diagnosis. | in review |
| 60 | Renal / Endocrine | Hyponatremia workup | Euvolemic man on clozapine with sodium 116 and confusion; next step. | in review |
| 61 | Social Sciences / Ethics | Substituted judgment at end of life | Dying cancer patient lacking capacity; wife reports he refused ventilation, daughter demands it; action. | in review |
| 62 | Blood & Lymphoreticular (Pediatrics) | Sickle cell disease newborn management | Five-day-old with FS hemoglobin pattern on newborn screen; next step. | in review |
| 63 | Endocrine (Pediatrics) | Congenital hypothyroidism | One-week-old with elevated TSH and low free T4 on confirmation; next step. | in review |
| 64 | Gastrointestinal | Appendicitis vs Crohn imaging | 18-year-old with migrating RLQ pain, intermittent diarrhea, leukocytosis; next diagnostic step. | in review |
| 65 | Reproductive / Obstetrics | Third-trimester bleeding / placenta previa | Third-trimester woman with heavy postcoital bleeding and no prenatal care; next step. | in review |
| 66 | Social Sciences / Ethics | Decision-making capacity vs power of attorney | Recovered patient with capacity prefers home care; son with POA insists on nursing home; next step. | in review |
| 67 | Nervous System | Hypertensive intracerebral hemorrhage | Hypertensive man with acute left hemiplegia and CT hyperdensity in right putamen; cause. | in review |
| 68 | Reproductive / Infectious | Bacterial vaginosis and post-procedure infection | Woman undergoing suction curettage has homogeneous gray discharge with pH 5.5; strongest infection risk factor. | in review |
| 69 | Musculoskeletal | Acute gout | Elderly diabetic on thiazide with sudden severe great-toe pain (photo); diagnosis. | in review |
| 70 | Cardiovascular | Silent ischemia in diabetes | Long-standing type 1 diabetic with neuropathy has painless 3-mm ST depression on stress test; diagnosis. | in review |
| 71 | Cardiovascular | Alcohol-induced hypertension | Young soldier drinking six beers daily with new elevated blood pressure; most likely cause. | in review |
| 72 | Skin / Infectious | Kaposi sarcoma | Man with painless arm rash (photo), weight loss, tachycardia; cause of dermatologic findings. | in review |
| 73 | Reproductive / Endocrine | Perimenopause / ovarian insufficiency | 42-year-old smoker with 6 months amenorrhea, hot flashes, palpitations; next diagnostic step. | in review |
| 74 | Social Sciences / Professionalism | Impaired physician | Colleague notices physician appears intoxicated during clinic hours; most appropriate action. | in review |
| 75 | Renal / Urinary | Transient proteinuria | Woman with proteinuria during UTI now has normal repeat urinalysis; additional study needed. | in review |
| 76 | Skin / Infectious / Surgery | Necrotizing fasciitis | Young man with rapidly worsening leg pain, cellulitis, hemorrhagic bullae, tachycardia after minor scratch; next step. | in review |
| 77 | Reproductive / Endocrine | Early gestational diabetes screening | Obese woman with prior macrosomic infants and diabetic parents at first prenatal visit; next step. | in review |
| 78 | Social Sciences / Geriatrics | Elder neglect | Previously controlled elderly diabetic now unkempt, missing visits, hyperglycemic after son moves in; diagnosis. | in review |
| 79 | Nervous System / Infectious | Lyme neuroborreliosis | New Jersey teen with facial palsy, headache, neck stiffness, lymphocytic CSF; next diagnostic step. | in review |
| 80 | Respiratory (Pediatrics) | Croup with stridor at rest | Toddler with barking cough, hoarseness, retractions, inspiratory stridor at rest; initial pharmacotherapy. | in review |

### Block 3

| # | System | Topic | What the item asks | Explanation |
|---|---|---|---|---|
| 81 | Renal / Surgery | Postoperative oliguria evaluation | Post-nephrectomy trauma patient with abrupt drop in bloody urine output; next step after saline. | in review |
| 82 | Patient Safety | Diagnostic error types | Physician labels wheelchair-bound teen with gastroenteritis without full exam; volvulus found later; error type. | in review |
| 83 | Behavioral Health / Pharmacology | Antidepressant selection with epilepsy | Man with depression, insomnia, and well-controlled epilepsy; most appropriate pharmacotherapy. | in review |
| 84 | Reproductive | Tubal factor infertility | Woman with prior ruptured appendix and PID, ovulatory cycles, HSG images shown; likely course untreated. | in review |
| 85 | Reproductive / Oncology | Ductal carcinoma in situ | Asymptomatic woman with a cluster of pleomorphic microcalcifications on screening mammogram; diagnosis. | in review |
| 86 | Patient Safety / Quality Improvement | Improving guideline adherence | Clinic performs annual asthma PFTs in only 34% of patients; procedure most likely to improve adherence. | in review |
| 87 | Reproductive / Infectious | Lactational mastitis | Breastfeeding woman 3 weeks postpartum with fever and wedge-shaped breast erythema; next step. | in review |
| 88 | Endocrine (Pediatrics) | Normal pubertal timing | 12-year-old girl with no breast development or pubic hair, otherwise well; next diagnostic step. | in review |
| 89 | Endocrine | Factitious hypoglycemia | Woman with hypoglycemic episodes, very high insulin but low C-peptide; expected abdominal CT finding. | in review |
| 90 | Patient Safety / Teamwork | Shared mental model in ICU teams | ICU wants to maintain a common mental model across team members; best method. | in review |
| 91 | Renal / Urinary (Pediatrics) | First febrile UTI imaging | 12-month-old with first febrile E. coli UTI responding to antibiotics; next step. | in review |
| 92 | Respiratory / Infectious | Adult pertussis | Man with weeks of paroxysmal cough and post-tussive vomiting after URI; pharmacotherapy. | in review |
| 93 | Respiratory / Infectious | Cystic fibrosis exacerbation | CF teen with purulent sputum, fever, hypoxemia, bibasilar consolidation (chart format); next evaluation step. | in review |
| 94 | Musculoskeletal | Hereditary multiple exostoses | Teen with EXT1 mutation and stable tibial bone polyps after minor knee injury; activity and workup recommendation. | in review |
| 95 | Gastrointestinal | Diverticular bleeding | Elderly woman with painless episodes of bright red rectal bleeding, hemodynamically stable; diagnosis. | in review |
| 96 | Behavioral Health (Pediatrics) | Normal adolescent development | 14-year-old with new peer group, curfew arguments, irritability, one trespassing episode; explanation for behavior. | in review |
| 97 | Renal / Urinary (Pediatrics) | Pediatric nephrolithiasis | Boy with acute colicky flank pain, hematuria, and hydronephrosis with hydroureter; next evaluation step. | in review |
| 98 | Respiratory | Hypersensitivity pneumonitis | Young lumber-mill worker with months of cough, weight loss, upper-lobe reticulonodular pattern, mixed PFTs. | in review |
| 99 | Behavioral Health / Nervous System | Psychogenic nonepileptic seizures | Woman with prolonged eyes-closed convulsive episodes, no EEG correlate, abuse history; next step. | in review |
| 100 | Immune (Pediatrics) | DiGeorge syndrome immunodeficiency | Toddler with cleft palate, VSD, recurrent infections, chest x-ray shown; expected leukocyte finding. | in review |
| 101 | Reproductive / Obstetrics | Rh prophylaxis at 28 weeks | Rh-negative woman at 28 weeks with weak anti-D after earlier immune globulin; next step. | in review |
| 102 | Skin / Immune (Pediatrics) | Poison ivy contact dermatitis | Child with itchy linear rash on forearm, cheek, ankle after a park picnic (photo); what avoidance would prevent it. | in review |
| 103 | Blood & Lymphoreticular | Chronic myeloid leukemia | Woman with fatigue, early satiety, splenomegaly, WBC 67,000 with left shift and basophilia (chart format). | in review |
| 104 | Respiratory | COPD diagnosis | Long-term smoker with progressive dyspnea, chronic cough, wheezes, prolonged expiration; next diagnostic step. | in review |
| 105 | Behavioral Health / Pharmacology | GAD treatment with alcohol use history | Unemployed man with months of worry, tension, insomnia, and prior alcohol use disorder; pharmacotherapy. | in review |
| 106 | Nervous System | REM sleep behavior disorder | Man acting out dreams violently with constipation history; greatest future risk. | in review |
| 107 | Social Sciences / Geriatrics | Elder abuse reporting | Demented woman with unexplained wrist fracture, multiple bruises, poor hygiene, sole caregiver son; next step. | in review |
| 108 | Cardiovascular / Toxicology | Methamphetamine cardiomyopathy | Young man with new heart failure, exertional chest pain, severe gingivitis; substance used. | in review |
| 109 | Endocrine | Pheochromocytoma confirmation | Hypertensive man with episodic headache, palpitations, sweating and adrenal mass on CT; next step. | in review |
| 110 | Gastrointestinal / Social Sciences | Recurrent alcoholic pancreatitis | Woman with recurrent pancreatitis, alcohol use disorder, and insecure housing; recommendation most reducing readmission. | in review |
| 111 | Skin (Pediatrics) | Miliaria | Boy in extreme heat with superficial clear fragile vesicles on the back without erythema; recommendation. | in review |
| 112 | Behavioral Health / Cardiovascular | Post-MI depression prognosis | Woman 3 months post-MI with new major depression; expected effect on overall health. | in review |
| 113 | Gastrointestinal | Zenker diverticulum | Elderly man with years of regurgitating undigested food, now aspiration pneumonia; cause of dysphagia. | in review |
| 114 | Reproductive | Functional ovarian cyst | Woman with mild LLQ pain, negative pregnancy test, 3x4 cm adnexal cyst, stable vitals; next step. | in review |
| 115 | Special Senses | Asymptomatic cerumen impaction | Woman with canals full of cerumen but normal hearing and no symptoms; next step. | in review |
| 116 | Respiratory | Pulmonary infarction | Post-oophorectomy woman with pleuritic pain, hemoptysis, wedge-shaped pleural density, no visible emboli; diagnosis. | in review |
| 117 | Cardiovascular / Surgery | Ruptured abdominal aortic aneurysm | Elderly heavy smoker with sudden abdominal pain, shock, diminished leg pulses, abdominal x-ray shown; diagnosis. | in review |
| 118 | Nervous System (Pediatrics) | Myelomeningocele complications | Newborn after myelomeningocele repair with paraplegia and mild ventriculomegaly; most likely associated finding. | in review |
| 119 | Biostatistics / Epidemiology | Extrapolation from surrogate endpoints | Trial shows fewer VT episodes with new drug; authors claim reduced mortality; flaw. | in review |
| 120 | Endocrine | Subacute (de Quervain) thyroiditis | Woman with sore throat, tender anterior neck fullness, low-grade fever, tachycardia, normal CBC; diagnosis. | in review |

## Explanations

3 of 120 explanations are published; the rest are in review.

### Item 1 -- Panic disorder with agoraphobia

*College student with recurrent panic attacks now avoiding public places and dates; most likely diagnosis.*

## What the item is testing

Two things are happening in this vignette and the question asks you to name the one that has taken over. Discrete attacks of terror with autonomic symptoms are panic attacks. The change the stem highlights is behavioural: the patient has started avoiding situations, and the avoidance is now shaping how she lives. Recognising which of those the diagnosis turns on is the item.

## The reasoning

Agoraphobia is defined by fear or avoidance of situations from which escape might be difficult or help unavailable if panic-like symptoms occurred. The classic settings are public transport, open spaces, enclosed spaces, queues and crowds, and being outside the home alone; the diagnosis needs fear of two or more of these, lasting months, out of proportion to any real danger, and causing genuine impairment. What makes the label fit here is that the avoidance is anticipatory. She is not avoiding a specific feared object; she is avoiding places where an attack would be humiliating or inescapable, and that fear of the attack is doing the driving.

Panic disorder and agoraphobia are separate diagnoses in DSM-5 and frequently coexist, so a patient with both is given both labels. When a question asks what best explains a shrinking social life, the answer is the condition that describes the avoidance, not the condition that describes the attacks.

## Why the other directions fail

Social anxiety disorder centres on being scrutinised or judged, so the fear tracks the presence of an audience rather than the difficulty of escape. Specific phobia attaches to one object or situation and does not generalise across public settings. Generalised anxiety disorder is diffuse worry about everyday matters without this pattern of situational avoidance. Depression can withdraw a patient from the world, but the stem's motive is fear of an attack, not loss of interest.

## The pattern to keep

Ask what the patient is avoiding and why. Escape and rescue point to agoraphobia; judgement points to social anxiety; a single trigger points to a specific phobia.

**Sources**

- USMLE Step 2 CK sample test questions (booklet updated July 2023), item 1 and its answer key: https://www.usmle.org/exam-resources/step-2-ck-materials/step-2-ck-sample-test-questions
- American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed., text revision (DSM-5-TR). 2022. Panic disorder and agoraphobia.
- Roy-Byrne PP, Craske MG, Stein MB. Panic disorder. Lancet. 2006;368(9540):1023-1032.

### Item 2 -- Paradoxical embolism workup

*Young man with MCA stroke while lifting weights plus leg swelling; normal carotids; next diagnostic step.*

## What the item is testing

A young patient with a large-vessel territory infarct and no atherosclerotic risk factors forces you to explain where the clot came from. The stem adds two clues that only make sense together: a swollen leg, and the fact that the event happened during heavy exertion. The question asks for the next diagnostic step, so you have to name the mechanism before you can choose the test.

## The reasoning

A venous clot in the leg travels to the right heart and normally stops in the pulmonary circulation. It reaches the brain only if there is a right-to-left communication, and the common one is a patent foramen ovale, present in roughly a quarter of adults and usually silent. Straining against a closed glottis -- which is what lifting heavy weights involves -- transiently raises right atrial pressure above left, opening the flap and letting venous material cross into the systemic circulation. That is paradoxical embolism, and it explains a stroke in a young person with clean carotids.

The test that demonstrates the shunt is echocardiography with agitated saline. Microbubbles injected into a peripheral vein opacify the right atrium; their prompt appearance in the left atrium within a few cardiac cycles, especially with a provocative Valsalva, shows the intracardiac shunt. Bubbles arriving late suggest an intrapulmonary shunt instead. The same study also looks for the other cardiac sources a young stroke deserves to have excluded.

## Why the other directions fail

Repeating carotid imaging adds nothing once it is normal, and carotid disease does not explain a coexisting leg clot. Prolonged rhythm monitoring is the right instinct for cryptogenic stroke in an older patient, but atrial fibrillation does not account for the venous findings here. A hypercoagulable panel may follow, yet it identifies why a clot formed rather than how it reached the brain, and results drawn during an acute event are hard to interpret.

## The pattern to keep

Young stroke plus venous thrombosis plus a Valsalva-type trigger means look for a shunt, and the bubble study is how you look.

**Sources**

- USMLE Step 2 CK sample test questions (booklet updated July 2023), item 2 and its answer key: https://www.usmle.org/exam-resources/step-2-ck-materials/step-2-ck-sample-test-questions
- Saver JL. Cryptogenic stroke. N Engl J Med. 2016;374(21):2065-2074.
- Kleindorfer DO, Towfighi A, Chaturvedi S, et al. 2021 Guideline for the prevention of stroke in patients with stroke and transient ischemic attack. Stroke. 2021;52(7):e364-e467.

### Item 3 -- Amiodarone pulmonary toxicity

*Man on multiple cardiac drugs with progressive dyspnea, dry cough, bilateral fine crackles; culprit medication.*

## What the item is testing

A patient on a cardiac drug list develops breathlessness that has crept up over months, a cough that brings nothing up, and fine crackles at both bases. The pattern is interstitial, not obstructive and not infective, and the item asks which of the drugs he is taking did it. Recognising the syndrome is only half the work; the other half is knowing which cardiac medication owns it.

## The reasoning

Amiodarone is highly lipophilic, concentrates in lung tissue and has a half-life measured in weeks, so its adverse effects accumulate with total dose and duration rather than appearing after the first tablets. Pulmonary toxicity is the most feared of them. The usual presentation is exactly this: subacute dyspnoea on exertion over weeks to months, non-productive cough, sometimes low-grade fever and weight loss, with bilateral inspiratory crackles. Imaging shows diffuse or patchy interstitial opacities, and pulmonary function testing shows a restrictive pattern with a reduced diffusing capacity -- a fall in that value is the earliest objective change and is why baseline and periodic testing are recommended.

Management is to stop the drug, in consultation with whoever is managing the arrhythmia, and to consider corticosteroids when disease is extensive; the alternative is progression to fibrosis. The same accumulation explains amiodarone's other organ toxicities, thyroid and hepatic, which are worth checking in the same visit.

## Why the other directions fail

An ACE inhibitor causes a dry cough, but from bradykinin accumulation, without crackles, hypoxaemia or interstitial change. Beta blockers can provoke bronchospasm in a patient with reactive airways, which is wheeze and obstruction rather than fine basal crackles. Statins cause myopathy, not interstitial lung disease. Heart failure itself produces crackles, but with orthopnoea, oedema and a raised venous pressure, and the stem's dry cough with a clear volume status points elsewhere.

## The pattern to keep

Slow-onset dyspnoea plus a dry cough plus bibasilar crackles in a patient on long-term antiarrhythmic therapy is amiodarone until proven otherwise. Ask for the diffusing capacity.

**Sources**

- USMLE Step 2 CK sample test questions (booklet updated July 2023), item 3 and its answer key: https://www.usmle.org/exam-resources/step-2-ck-materials/step-2-ck-sample-test-questions
- Wolkove N, Baltzan M. Amiodarone pulmonary toxicity. Can Respir J. 2009;16(2):43-48.
- Vassallo P, Trohman RG. Prescribing amiodarone: an evidence-based review of clinical indications. JAMA. 2007;298(11):1312-1322.

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