USMLE STEP 2 CK

A 56-year-old right-handed warehouse worker presents after attempting to lift a heavy box from shoulder height. He felt a sudden painful 'pop' in the front of his right shoulder followed by immediate weakness and bruising over the upper arm. He now notices a bulge in the lower arm ('Popeye' deformity) and has difficulty with elbow flexion and forearm supination. He has a history of chronic shoulder pain consistent with rotator cuff tendinopathy and recently received a corticosteroid injection. Examination reveals ecchymosis over the proximal arm, tenderness in the bicipital groove, a positive Speed test before injury history, mild weakness of elbow flexion, marked weakness of supination, and a visible distal bulge of the biceps muscle. Neurovascular examination is normal. Shoulder radiographs show no fracture.

Which patient is most likely to benefit from early surgical repair?

A 31-year-old man who has sex with men presents for routine care. He reports receptive anal and oral intercourse with several partners during the past year. He is asymptomatic and requests comprehensive STI screening.

Which approach is most appropriate for gonorrhea and chlamydia screening?

A 54-year-old postmenopausal G2P2 woman presents after noticing a painless lump in her left breast 2 months ago. The mass has gradually enlarged. She denies fever or trauma but reports occasional bloody nipple discharge. Menarche occurred at age 11 and menopause at age 53. She had her first pregnancy at age 34. Her mother was diagnosed with breast cancer at age 45. She has obesity, drinks 2 glasses of wine daily, and used combined menopausal hormone therapy for 6 years. Physical examination reveals a firm, irregular, nonmobile 2.8-cm mass in the upper outer quadrant of the left breast with ipsilateral palpable axillary lymphadenopathy and mild nipple retraction. Diagnostic mammography demonstrates a spiculated mass with pleomorphic calcifications (BI-RADS 5). Targeted breast ultrasound confirms a solid hypoechoic irregular lesion. Ultrasound-guided core needle biopsy shows invasive ductal carcinoma. Immunohistochemistry for ER, PR, and HER2 is pending.

Which biomarker profile is routinely obtained because it directly guides systemic therapy?

A 39-year-old corporate executive is referred for psychiatric evaluation after repeated conflicts with coworkers. He describes himself as exceptionally talented and says that ordinary workplace rules should not apply to him because of his importance. He frequently exaggerates his accomplishments, expects special treatment, and becomes angry when colleagues do not immediately comply with his requests. He seeks admiration from senior executives and spends considerable time fantasizing about extraordinary success, power, and recognition. He routinely takes credit for his team's work and appears indifferent when told that his behavior has harmed coworkers. When his supervisor recently criticized a presentation, he responded with intense humiliation, rage, and accusations that the supervisor was incompetent and jealous. This pattern has been present since early adulthood across occupational and interpersonal settings. He has no episodes of mania, psychosis, or substance intoxication.

Why can criticism provoke intense anger or humiliation in patients with this disorder?

A previously healthy 9-month-old boy is brought to the emergency department because of sudden episodes of intense crying and drawing his knees toward his chest. The episodes began 8 hours ago and initially occurred every 20 to 30 minutes, with the infant appearing relatively comfortable between attacks. Over the past 3 hours, the episodes have become more frequent and he has had three episodes of nonbilious vomiting. His mother also noticed a small amount of dark red mucus in the diaper. He had an upper respiratory infection 1 week ago but has no history of abdominal surgery, congenital anomalies, or prior gastrointestinal disease.

Temperature is 37.7°C, blood pressure is 92/56 mm Hg, pulse is 132/min, respiratory rate is 24/min, and oxygen saturation is 99% on room air. He appears intermittently irritable but is consolable between painful episodes. The abdomen is mildly distended. During a quiet interval, palpation reveals a sausage-shaped mass in the right upper quadrant and relative emptiness of the right lower quadrant. There is no rebound tenderness, guarding, or rigidity. Rectal examination reveals mucus streaked with dark red blood.

Laboratory studies show WBC 12,900/mm³, hemoglobin 11.3 g/dL, sodium 136 mEq/L, potassium 4.0 mEq/L, bicarbonate 22 mEq/L, and creatinine appropriate for age. Abdominal ultrasonography demonstrates a concentric multilayered 'target' or 'doughnut' appearance in the right upper abdomen consistent with ileocolic intussusception. There is preserved bowel-wall perfusion and no free intraperitoneal air.

What is the most appropriate next step in management?