1
Q
Lung mass of a nonsmoker genes
A
EGFR and ALK
2
Q
Lung mass of a nonsmoker
A
Adenocarcinoma
3
Q
Mass in the lung with a keratin pearl
A
squamous cell carcinoma
4
Q
This is found in the lung- what type of cancer
A
Small cell lung cancer arises in a blue cells with scant cytoplasma nd indistinct nucleui
5
Q
Which lung cancers are central
A
Suqamous cell carcinoma and small cell carcinoma
6
Q
What are klutichsky cells
A
Dark purple neuroendocrine cells found in small cell carcinoma
7
Q
Small cell lung cancer oncogene
A
L-myc
8
Q
What are the markers of small cell lung cancer
A
Chromagranin, Synaptophysin, NCAM, CD56,
9
Q
Small cell lung cancer is associated with what conditions
A
SIADH, Lambert Eaton, Cushing Syndrome
10
Q
What is a superior sulcus tumor
A
A pancoast tumor
11
Q
Clubbing of the fingers is most likely associated with
A
Lung cancer
12
Q
Nail pitting is associated with
A
psoriasis
13
Q
Koilonychia is associated with
A
theyre spoon nails and iron deficience
14
Q
Half and Half nails aka Lindsay nails
A
Chronic renal failure
15
Q
In PE what hppeens to PaO2 and PaCO2 and PH
A
lower PaO2 and PCo2 and higher pH due to hyperventilatio nand normal HCO3
16
Q
A perfusion defect without ventilation defect
A
PE
17
Q
Does PCO2 increase or decrease Ph!
A
More PCO2 = decrease Ph
18
Q
Type I pneumocytes
A
Squamous. 97% of alveolar surfaces. Thinly line
the alveoli (two black arrows in A) for optimal
gas exchange.
19
Q
Type II pneumocytes
A
Cuboidal and clustered A.
2 functions:
1. Serve as stem cell precursors for 2 cell
types (type I and type II cells); proliferate
during lung damage.
2. Secrete surfactant from lamellar bodies
(arrowheads in B).
Surfactant— alveolar surface tension,
alveolar collapse, lung recoil, and
compliance.
Composed of multiple lecithins, mainly
dipalmitoylphosphatidylcholine (DPPC).
Synthesis begins ~20 weeks’ gestation and
achieves mature levels ~35 weeks of gestation.
Corticosteroids important for fetal surfactant
synthesis and lung development.
2 (surface tension) Collapsing pressure (P) = radius
Law of Laplace—Alveoli have tendency to
collapse on expiration as radius .
Alveolar macrophages Phagocytose foreign materials; release cytokines
and alveolar proteases. Hemosiderin-laden
macrophages (heart failure cells) may be found
in the setting of pulmonary edema or alveolar
hemorrhage.
20
Q
What are the key physiological changes and adaptations to high altitude?
A
- At high altitude:
↓ Atmospheric O₂ (↓ PiO₂ → ↓ PaO₂)
↑ Ventilation → ↓ PaCO₂ → Respiratory alkalosis
Acute symptoms: headache, nausea, fatigue, lightheadedness, sleep disturbance
Chronic adaptations:
Sustained ↑ ventilation
↑ Erythropoietin → ↑ Hct & Hb (response to chronic hypoxia)
↑ 2,3-BPG → rightward shift of O₂ dissociation curve → ↑ O₂ release to tissues
Cellular changes: ↑ mitochondria density
Renal compensation: ↑ excretion of HCO₃⁻ (can be augmented with acetazolamide)
Chronic hypoxic pulmonary vasoconstriction → ↑ pulmonary vascular resistance → pulmonary hypertension → right ventricular hypertrophy (RVH)
21
Q
A 28-year-old previously healthy man comes to the urgent care clinic due to shortness of breath. The patient is on a ski vacation in Breckenridge, Colorado, which is situated at an altitude of 2926 m (9600 ft). On arrival 4 days ago, he experienced mild headache and nausea that resolved spontaneously, but since yesterday, he has had worsening dyspnea and cough. The patient now feels short of breath even with minimal exertion. Temperature is 37.3 C (99.1) F, blood pressure is 134/82 mm Hg, pulse is 98/min, and respirations are 22/min. Oxygen saturation is 86% on ambient air, which rapidly improves to 95% with supplemental oxygen. Physical examination shows pink mucous membranes, flat neck veins, bilateral inspiratory crackles, and no heart murmurs or pedal edema. Chest x-ray reveals patchy alveolar infiltrates. Which of the following is the most likely cause of this patient’s current condition?
A. Alveolar-capillary membrane disruption
B. Embolic pulmonary arterial occlusion
C. Excessive decrease in PaCO2 level
D. Impaired left ventricular function
E. Increased total red blood cell mass
A
A. Alveolar-capillary membrane disruption
22
Q
AAT deficiency causes early-onset panacinar emphysema, which predominantly affects
A
lower lung lobes.
23
Q
Interchain cross-links involving _____ give elastin its elastic recoil property.
A
lysine (formed by lysyl oxidase)
24
Q
What are the classic pulmonary examination findings in pleural effusion regarding breath sounds, tactile fremitus, and percussion?
A
Breath sounds: Decreased or absent
Tactile fremitus: Decreased
Percussion: Dullness
25
According to Light’s criteria, a pleural effusion is exudative if any of the following are true:
Pleural fluid protein / serum protein > 0.5
Pleural fluid LDH / serum LDH > 0.6
Pleural fluid LDH > 2/3 the upper limit of normal serum LDH
If none are met → transudative effusion.
26
Sabouraud agar has a pH of ~5.6 and high glucose content. What type of organisms does this favor?
Fungi (yeasts and molds), because acidic pH inhibits bacterial growth.
26
What are typical lab findings in transudative vs exudative pleural effusions?
Feature Transudate Exudate
Protein Low (< 3 g/dL, PF/S < 0.5) High (> 3 g/dL, PF/S > 0.5)
LDH Low (< 200 U/L, PF/S < 0.6) High (> 200 U/L, PF/S > 0.6)
Appearance Clear, straw-colored Cloudy, sometimes bloody or purulent
WBCs < 1000, mostly mononuclear Usually higher, often neutrophils if infection
27
Which class of antifungals works by blocking ergosterol synthesis in fungal cell membranes?
Azoles (e.g., fluconazole, itraconazole).
28
A patient with tinea corporis is cultured on Sabouraud agar. Which oral antifungal works by inhibiting ergosterol synthesis?
Terbinafine (inhibits squalene epoxidase) or azoles (inhibit lanosterol demethylase).
29
A 22-year-old woman with a history of anorexia nervosa and intense exercise presents with secondary amenorrhea. She is admitted for nutritional rehabilitation. Within the first 48 hours of refeeding, which electrolyte is most likely to decrease first?
A) Sodium
B) Potassium
C) Phosphate
D) Calcium
E) Magnesium
Phosphate ✅
Explanation:
This patient is at risk for refeeding syndrome.
During starvation, insulin levels are low, and intracellular phosphate is depleted.
Refeeding (especially carbohydrates) causes a sudden rise in insulin → drives phosphate into cells for ATP production.
Result: Rapid hypophosphatemia.
Other electrolyte changes:
Potassium and magnesium may also fall, but phosphate is the first to decrease.
High-yield USMLE tip:
Watch for muscle weakness, respiratory failure, arrhythmias, or hemolysis in malnourished patients during initial nutrition.
30
31
Brown discoloration around the ankles with edema and ulceration
venous stasis dermatitis.
32
A 7-year-old presents with sore throat, fever, tonsillar exudates, and a sandpaper-like rash. Gram stain: β-hemolytic cocci in chains. Most likely organism?
Streptococcus pyogenes (GAS)
High-Yield Associations:
Pharyngitis / Tonsillitis
Scarlet fever (erythrogenic toxin)
Impetigo, cellulitis, erysipelas
Necrotizing fasciitis
Post-strep complications: rheumatic fever (pharyngitis only), post-strep glomerulonephritis
Lab Clues:
Bacitracin sensitive
PYR positive
33
A newborn develops sepsis and meningitis on day 2 of life. Blood culture: β-hemolytic, Gram-positive cocci in chains. Most likely organism?
Streptococcus agalactiae (GBS)
High-Yield Associations:
Neonatal sepsis & meningitis
UTIs in adult women
Lab Clues:
Bacitracin resistant
CAMP test positive
34
Chronic alcoholic presents with confusion, ataxia, and horizontal nystagmus. Most likely diagnosis?
Acute Wernicke Encephalopathy
Cause: Thiamine (B1) deficiency
Eye finding: horizontal gaze palsy / nystagmus
Treatment: IV thiamine (before glucose)
35
Which feature distinguishes acute Wernicke from chronic Korsakoff?
Acute Wernicke: confusion, ataxia, ophthalmoplegia / horizontal nystagmus
Chronic Korsakoff: memory loss, confabulation, mammillary body atrophy; eye signs absent
36
Why does mammillary body atrophy cause memory deficits?
Mammillary bodies are part of the Papez circuit
Damage → impaired hippocampus → mammillary body → anterior thalamus → cingulate gyrus pathway → anterograde amnesia
37
A patient on simvastatin develops muscle pain after starting erythromycin. Mechanism?
Erythromycin inhibits CYP3A4 → ↑ simvastatin levels → rhabdomyolysis
Statins metabolized by CYP3A4: simvastatin, atorvastatin, lovastatin
Safer alternatives: pravastatin, rosuvastatin
38
Patient receives ketamine for procedural sedation. Mechanism of action?
Noncompetitive NMDA receptor antagonist → blocks glutamate → dissociative anesthesia
Effects: analgesia, amnesia, sedation
Sympathomimetic: ↑ HR, BP, CO
Minimal respiratory depression
39
Pseudopalisading necrosis, nuclear pleomorphism, microvascular proliferation in an adult brain tumor.
Glioblastoma multiforme (GBM)
WHO Grade IV astrocytoma
Most common in adults, usually frontal/temporal lobe
Highly malignant, poor prognosis
40
“Fried-egg” cells and “chicken-wire” capillary pattern on histology; usually frontal lobe.
Oligodendroglioma
Slow-growing, often frontal lobe
Calcifications common
Better prognosis than astrocytomas
41
Rosenthal fibers (eosinophilic corkscrew fibers) in a pediatric cerebellar tumor.
Pilocytic astrocytoma (WHO Grade I)
Benign, slow-growing
Most common in children, cerebellum
Good prognosis with surgical resection
42
Homer Wright rosettes in a midline cerebellar tumor in a child.
Medulloblastoma
Highly malignant, primitive neuroectodermal tumor (PNET)
Common in children, midline cerebellum
Can metastasize via CSF
43
Spindle-shaped cells in whorled pattern with psammoma bodies on histology.
Meningioma
Extra-axial, slow-growing, often convexities, falx, sphenoid wing
Usually benign, can cause mass effect
44
Perivascular pseudorosettes in a tumor lining the ventricles.
Ependymoma
Often arises from 4th ventricle in children, spinal cord in adults
Can cause hydrocephalus
45
A woman on metoclopramide develops secondary amenorrhea and galactorrhea. Mechanism?
Metoclopramide blocks D2 receptors → ↑ prolactin → inhibits GnRH → ↓ FSH/LH → anovulation → amenorrhea
46
A patient presents with left-sided numbness of the face and extremities, no motor deficits. Most likely lacunar infarct location?
Right thalamus (VPL/VPM) → pure sensory stroke
Often due to small vessel disease (hypertension, diabetes)
47
Painless scrotal swelling that transilluminates, anterior to the testis.
Hydrocele
Fluid between tunica vaginalis layers
Transilluminates brightly
Usually congenital in infants or acquired in adults
48
Painless mass superior/posterior to testis that may transilluminate.
Spermatocele
Cyst in epididymal head containing sperm
Transilluminates slightly opaque
Usually asymptomatic
49
“Bag of worms” mass above testis, worse with standing/valsalva.
Varicocele (dilated pampiniform plexus)
Does not transilluminate
More common on left side (drains into left renal vein)
Can cause infertility
50
A postmenopausal woman with osteoporosis and a history of DVT is seeking treatment. Which drug is safest?
Alendronate (bisphosphonate) ✅
Avoid: Estrogen, raloxifene ❌ (VTE risk)
Testosterone only if male and hypogonadal
51
postmenopausal woman with osteoporosis has a history of deep vein thrombosis. She is now seeking treatment to reduce fracture risk. Which of the following medications is most appropriate for her?
A. Alendronate
B. Estrogen
C. Lovastatin
D. Raloxifene
E. Testosterone
Answer:
A. Alendronate ✅
Explanation:
Alendronate: Safe first-line treatment for osteoporosis; reduces fracture risk.
Estrogen & Raloxifene: Increase risk of venous thromboembolism → contraindicated in patients with prior DVT.
Lovastatin: Not used for osteoporosis.
Testosterone: Only indicated in men with hypogonadism.
52
Patient has thickened, white, flaking nails. Nail scrapings reveal elongated, pencil-shaped macroconidia and no microconidia. Etiologic agent?
Epidermophyton floccosum ✅
Club-shaped macroconidia, smooth-walled, multicellular
Causes tinea pedis, tinea cruris, sometimes onychomycosis
Unlike Trichophyton → no microconidia
53
A 3-year-old develops acute lower limb weakness after a viral illness. Where does the pathological agent primarily act?
Anterior horn cells ✅
Mechanism: virus infects motor neurons → flaccid paralysis
Signs: hypotonia, hyporeflexia, asymmetric weakness
Classic agent: poliovirus
54
A 1-month history of severe diarrhea is accompanied by perianal pain, fissures, scarring, sinus tracts, and fistulas. Most likely diagnosis?
Transmural inflammation
Can affect any part of GI tract (skip lesions)
Perianal disease common
Differentiation from UC: UC → continuous mucosal disease, rarely perianal fistulas
55
A patient presents with fatigue, weakness, 8 lb weight loss, hypotension, hyponatremia, hyperkalemia, and elevated creatinine. Most likely diagnosis?
Primary adrenal insufficiency (Addison’s disease) ✅
Labs: ↓ Na⁺, ↑ K⁺, ↑ creatinine
Mechanism: ↓ aldosterone → salt wasting; ↓ cortisol → hypotension, fatigue
Causes: autoimmune (most common in developed countries), infections (TB in developing countries)
Primary adrenal insufficiency (Addison’s disease):
Destruction of adrenal cortex → ↓ cortisol & ↓ aldosterone
↓ Aldosterone → Na⁺ loss, K⁺ retention → hyponatremia, hyperkalemia
↓ Cortisol → hypotension, fatigue, weakness
Can lead to prerenal acute kidney injury → ↑ creatinine
56
A patient has 3 weeks of lateral elbow pain, worse with tennis, radial head posterior, and pain with wrist extension. Mechanism?
Overuse of wrist extensors → microtears at lateral epicondyle (tennis elbow) ✅
Force transmitted to radial head → posterior pain/displacement
Mechanism: repetitive wrist extension, especially backhand stroke
57
Uterus contains sharply circumscribed, discrete, round, firm, gray-white nodules ~5 cm. Most likely diagnosis?
Leiomyoma (uterine fibroid) ✅
Benign smooth muscle tumor of myometrium
Usually firm, well-circumscribed, gray-white
May cause menorrhagia, infertility, pelvic pressure
58
Woman with dysmenorrhea, menorrhagia, diffusely enlarged boggy uterus. Histology: endometrial glands in myometrium. Diagnosis?
Adenomyosis ✅
59
A patient uses an over-the-counter agent and develops flatulence, abdominal distention, and profuse diarrhea. Mechanism?
lactulose- Osmotic diarrhea due to non-absorbable sugar or magnesium salts ✅
Mechanism: solute in gut lumen draws water → diarrhea; bacterial fermentation → gas
Common agents: lactulose, sorbitol, magnesium hydroxide
60
A patient starts prazosin for BPH and experiences dizziness and lightheadedness upon standing. Mechanism?
Alpha-1 blockade → vasodilation → impaired compensatory vasoconstriction → orthostatic hypotension ✅
61
12-year-old girl with heavy periods, purpura, epistaxis, gingival bleeding. Labs: normal platelet count, prolonged bleeding time. Diagnosis?
Glanzmann thrombasthenia (GPIIb/IIIa defect, impaired platelet aggregation) ✅
62
Boy with hemarthroses and muscle hematomas after minor trauma. Labs: prolonged aPTT, normal PT, normal platelets. Diagnosis?
: Hemophilia A (Factor VIII deficiency)
63
Two soldiers with neck scratches from civilian fur collars, develop pruritic papules → necrotic ulcers (black eschar), mild fever and malaise. Gram-positive aerobic rods seen. Most likely pathogen?
Bacillus anthracis (cutaneous anthrax) ✅
Exposure: contaminated animal hides/fur/wool
Key features: painless necrotic eschar, mild systemic symptoms
Gram stain: aerobic Gram-positive rods
64
Teenager with 2-month history of facial cysts and white papules after starting a new face wash. Histology shows what?
A) Comedones filled with sebum and keratin
B) Deposits of complements at the dermoepidermal junction
C) Epidermal hyperplasia and koilocytes
D) Microabscess
E) Folliculitis
Classic for acne vulgaris
Pathophysiology: follicular hyperkeratinization + sebum accumulation → comedone formation
Other options:
B → Lupus (dermoepidermal junction complement deposits)
C → HPV/warts (koilocytes)
D → Pustular bacterial lesions (not classic acne histology)
E → Folliculitis (usually bacterial/fungal, not typical acne pattern)
65
23-year-old with memory loss, violent behavior, and hygiene neglect. You start pharmacologic therapy for Alzheimer’s. What is the mechanism of the first-line drugs?
B) Acetylcholinesterase inhibition ✅
Drugs: Donepezil, Rivastigmine, Galantamine
Mechanism: increase acetylcholine in synaptic cleft → improve cognition and behavior
NMDA blockade (Memantine) is second-line or adjunct
Alzheimer’s pathology:
Loss of basal forebrain cholinergic neurons, especially in the nucleus basalis of Meynert
Leads to decreased acetylcholine (ACh) in the hippocampus and cortex
Result: impaired memory, attention, and learning
Role of acetylcholine:
ACh is critical for cortical activation, memory formation, and attention
Enhances synaptic plasticity in the hippocampus → facilitates encoding of new memories
65
Match the following reflexes to their spinal nerve roots:
Biceps
Brachioradialis
Triceps
Biceps: C5
Brachioradialis: C6
Triceps: C7
66
A 75-year-old man presents with fatigue, weight loss, and RUQ tenderness. He previously worked in a plastic pipe factory. Liver biopsy shows pleomorphic spindle cells positive for PECAM-1 (CD31). What is the most likely diagnosis?
Hepatic angiosarcoma
Hepatic angiosarcoma is a rare, aggressive vascular tumor of the liver associated with occupational exposure to vinyl chloride, arsenic, and Thorotrast (thorium dioxide). Tumor cells are of endothelial origin and express PECAM-1 (CD31).
67
What occupational and environmental exposures are classically associated with hepatic angiosarcoma?
Vinyl chloride (PVC industry, plastics)
Arsenic (pesticides, contaminated water)
Thorotrast (historical radiographic contrast)
Explanation:
These agents are potent carcinogens that induce endothelial mutations in hepatic sinusoids, leading to malignant vascular proliferation.
68
A rare, vascular, malignant tumor of the liver that is associated with exposure to ___
vinyl chloride, arsenic, and thorium dioxide.
69
An 84-year-old woman with an indwelling catheter and recurrent nephrolithiasis presents with confusion, fever, and alkaline urine (pH 8.5) that smells like ammonia. What organism is most likely responsible?
A: Proteus mirabilis
Explanation:
Gram-negative, oxidase-negative rod
Urease-positive → splits urea into ammonia and CO₂ → alkalinizes urine (↑ pH)
Ammonia odor in urine
Promotes formation of struvite (magnesium ammonium phosphate) stones
70
How does Proteus mirabilis cause stone formation and alkaline urine?
Urease enzyme converts urea → ammonia + CO₂
Ammonia raises urinary pH
Promotes precipitation of magnesium ammonium phosphate → struvite stones
71
What type of stones are associated with Proteus UTIs, and what are their characteristic features?
Struvite stones (magnesium ammonium phosphate)
Radiopaque
May form staghorn calculi
Often require surgical removal due to recurrent infection and obstruction
72
11-year-old boy from Nigeria
→ Jaw mass + cervical lymphadenopathy
→ Biopsy: sheets of lymphocytes with tingible body macrophages (“starry sky” pattern)
→ EBV serology positive
✅ Answer: t(8;14)
Diagnosis: Endemic (African) Burkitt lymphoma
73
Q: An 11-year-old boy from Nigeria presents with a jaw mass and EBV positivity. Biopsy shows a “starry sky” pattern. What is the diagnosis and associated translocation?
A:
Diagnosis: Endemic Burkitt lymphoma
Translocation: t(8;14)
Gene: c-MYC (chromosome 8) translocated to Ig heavy chain locus (chromosome 14)
74
Q: What is the molecular consequence of the t(8;14) translocation in Burkitt lymphoma?
c-MYC oncogene on chromosome 8 becomes overexpressed due to its placement next to the immunoglobulin heavy-chain promoter on chromosome 14
Leads to uncontrolled cellular proliferation
75
A 72-year-old man has progressive lower extremity weakness, urinary incontinence, and back pain. Imaging shows multiple sclerotic (osteoblastic) lesions in the spine. What is the most likely underlying malignancy?
Metastatic prostate adenocarcinoma
76
A pregnant woman from South Asia presents with acute liver failure (jaundice, elevated transaminases, coagulopathy, encephalopathy). Which viral marker is most likely elevated?
A: Anti-HEV IgM
Diagnosis: Acute Hepatitis E infection
77
What is the typical epidemiology of Hepatitis E virus (HEV)?
Transmission: Fecal–oral (contaminated water)
Regions: Developing countries in Asia, Africa, Mexico
Outbreaks: After heavy rains or poor sanitation
78
What type of virus is Hepatitis E?
Hepevirus family
Non-enveloped, single-stranded, positive-sense RNA virus
Replicates in the cytoplasm
79
A newborn with jaundice, anemia, splenomegaly, and echinocytes on blood smear most likely has a deficiency in what enzyme?
Pyruvate kinase deficiency → ↓ ATP production → membrane rigidity → extravascular hemolysis.
Mnemonic:
💡 “PK = Power (ATP) Keeper” — without PK, RBCs lose power → rigid → splenic destruction.
LDH leaks During Hemolysis” → L for Lactate, L for Leak, D for Destruction, H for Hemolysis.
80
What happens to LDH in hemolysis
LDH leaks During Hemolysis” → L for Lactate, L for Leak, D for Destruction, H for Hemolysis.
81
34-year-old archaeologist is concerned about premature skin aging from sun exposure. Which sunscreen ingredient provides broad-spectrum protection against both UVA and UVB radiation?
Zinc oxide (mineral-based sunscreen)
Key points:
UVA: penetrates deeper, causes photoaging and DNA damage
UVB: causes sunburn and contributes to skin cancer
Broad-spectrum sunscreens: zinc oxide, titanium dioxide → block both UVA & UVB
Chemical UVB-only blockers: PABA, trolamine salicylate, cinnamates → do not prevent photoaging
Mnemonic:
💡 “Zinc = Zenith of broad protection” → protects skin from both UVA and UVB.
82
: A 17-year-old presents with fever, sore throat, cervical lymphadenopathy, tonsillar exudates, palatal petechiae, and splenomegaly. Labs show lymphocytosis with atypical lymphocytes and a positive heterophile antibody test. Which condition is she at increased risk for?
Key points:
Primary infection: Epstein-Barr virus (EBV) → infectious mononucleosis
Symptoms: fever, pharyngitis, lymphadenopathy, splenomegaly, fatigue
Labs: lymphocytosis, atypical lymphocytes, positive heterophile antibody
Complications:
Hematologic malignancies: Hodgkin lymphoma, Burkitt lymphoma, diffuse large B-cell lymphoma
Nasopharyngeal carcinoma
Mechanism: EBV latent infection → LMP1 activates NF-κB, driving B-cell proliferation
Mnemonic:
💡 “EBV = Epstein’s Big Virus → Big risk for Hodgkin lymphoma”
83
Teardrop red blood cells
dacrocytes
84
A 65-year-old man presents with 6 months of fatigue and abdominal pain. Physical exam shows pallor and splenomegaly. Labs reveal Hb 9.1 g/dL, WBC 3,400/mm³. Peripheral smear shows teardrop cells and nucleated RBCs. Genetic testing is positive for a JAK2 mutation.
Question: What is the most likely underlying mechanism of this patient’s condition?
Answer: Fibrosis in the bone marrow
Explanation:
This patient has primary myelofibrosis (PMF), a myeloproliferative neoplasm.
Key features:
Teardrop RBCs (from extramedullary hematopoiesis)
Cytopenias (anemia, leukopenia)
Splenomegaly (extramedullary hematopoiesis)
JAK2 mutation → constitutive JAK-STAT activation
Pathophysiology:
Abnormal megakaryocytes release TGF-β and PDGF → marrow fibrosis
Fibrosis disrupts normal hematopoiesis → blood cells produced in spleen/liver
Other features: Fatigue, abdominal discomfort, risk of transformation to acute leukemia
85
2-month history of a cough productive of clear mucoid sputum. smoked one pack of cigarettes daily for 33 years. Chest x-ray shows a 2-cm solid nodule in the periphery of the lower left lobe. biopsy shows numerous mucin-filled epithelial cells lining the alveolar basement membrane. The cells have prominent nucleoli, coarse chromatin, and some cells have multiple nuclei. Which of the following is the most likely diagnosis?
adenocarcinoma of the lung
Key USMLE points:
Peripheral lung nodule in a smoker often adenocarcinoma
Mucin-producing tumor with lepidic growth pattern
Can present with clear sputum due to mucin production
Prognosis better than small cell, worse if invasive features are present
86
_______ is a complication of untreated group A streptococcal (GAS) infections such as scarlet fever and tonsillopharyngitis. MR is the result of rheumatic heart disease, which can cause early mitral regurgitation or prolapse and later evolves into mitral stenosis.
Mitral valve regurgitation (MR)
87
A 23-year-old woman with asthma presents with severe shortness of breath and wheezing. She is unable to speak in full sentences. Vital signs: pulse 116/min, respirations 28/min, O₂ sat 92% on room air. Lung exam shows decreased breath sounds with scattered end-expiratory wheezing. She is started on high-dose continuous inhaled albuterol.
Question: Which of the following adverse effects is she at increased risk for?
Hypokalemia
Explanation:
Mechanism:
Albuterol is a β2-adrenergic agonist → stimulates Na⁺/K⁺-ATPase → shifts K⁺ into cells, causing hypokalemia.
β2 stimulation also increases glycogenolysis → ↑ insulin → further drives K⁺ into cells.
Other effects of high-dose β2-agonists:
Tachycardia (β1 effect + reflex from vasodilation)
Tremor
Hypomagnesemia, hypophosphatemia
Clinical importance:
Hypokalemia can cause EKG changes: flattened T waves, ST depression, U waves
Severe hypokalemia can precipitate arrhythmias
Key USMLE Tip:
Continuous or high-dose β2-agonist therapy increases risk for electrolyte disturbances, especially hypokalemia, even in otherwise healthy patients.
88
A 28-year-old woman comes to the emergency department because of a 2-day history of dark urine, increasing abdominal pain, and a tingling sensation in her arms and legs. She has a history of epilepsy. Her current medication is phenytoin. She is nauseated and confused. Following the administration of hemin and glucose, her symptoms improve. The beneficial effect of this treatment is most likely due to inhibition of which of the following enzymes?
Aminolevulinate dehydratase
Aminolevulinate acid synthase
Ferrochelatase
Porphobilinogen deaminase
Uroporphyrinogen decarboxylase
ALA synthase
Acute intermittent porphyria is treated with hemin + glucose, which inhibit ALA synthase, reducing the production of neurotoxic heme precursors ALA and PBG.
89
A 29-year-old woman, gravida 1, para 0 at 11 weeks' gestation comes to the physician because of a 2-day history of left lower extremity pain and swelling. Her temperature is 37.9°C (100.2°F). Physical examination shows a tender, palpable cord on the lateral aspect of the left lower leg. The overlying skin is erythematous and indurated. Duplex ultrasound shows vascular wall thickening and subcutaneous edema. Which of the following is the most likely diagnosis?
Superficial thrombophlebitis
90
A 35-year-old woman presents with acute right flank pain and gross hematuria. She has had similar episodes in the past. Urinalysis shows blood, and 24-hour urine collection reveals wedge-shaped crystals. Serum uric acid is mildly elevated. Which of the following is most likely to prevent recurrence?
A. Low-potassium diet
B. High-protein diet
C. Amoxicillin/clavulanate
D. Dietary calcium restriction
E. Allopurinol
F. Chlorthalidone
F. Chlorthalidone for te wedge shapes stones of the calcium phosphate
91
wedge shapes stones
calcium phosphate
92
A 60-year-old man comes to the physician because his wife has noticed that his left eye looks smaller than his right. He has had worsening left shoulder and arm pain for 3 months. He has smoked two packs of cigarettes daily for 35 years. Examination shows left-sided ptosis. The pupils are unequal but reactive to light; when measured in dim light, the left pupil is 3 mm and the right pupil is 5 mm. Which of the following is the most likely cause of this patient's ophthalmologic symptoms?
Thrombosis of the cavernous sinus
Aneurysm of the posterior cerebral artery
Infarction of the hypothalamus
Dissection of the carotid artery
Compression of the stellate ganglion
Infiltration of the cervical plexus
Compression of the stellate ganglion
Compression of the stellate ganglion by a Pancoast tumor can lead to Horner syndrome via injury of preganglionic sympathetic fibers. Superior sulcus tumors can infiltrate neighboring structures and cause additional symptoms, which is known as Pancoast syndrome. This patient's shoulder and arm pain are likely symptoms of Pancoast syndrome, which also includes atrophy of the arm and hand muscles, and possibly superior vena cava syndrome and hoarseness due to compression of the recurrent laryngeal nerve. The most common cause of Pancoast syndrome is NSCLC, for which this patient is at risk because of his history of smoking.
93
Compression of the Stellate ganglion
Horner syndrome (ipsilateral ptosis, miosis, anhidrosis)
94
A 60-year-old woman comes to the physician because of palpitations and a 5.4-kg (11.9-lb) weight loss over the past 3 months. She appears anxious. Her pulse is 104/min and blood pressure is 148/101 mm Hg. Physical examination shows warm skin, mild tremor, and an enlarged thyroid gland. A thyroid scintigraphy scan shows several focal areas with increased uptake. A biopsy of one of these areas of affected thyroid tissue is most likely to show which of the following?
A. Sheets of parafollicular cells with amyloid stroma
B. Inflammatory infiltrate with multinucleated giant cells and granulomas
C. Follicle destruction with lymphocytic infiltrate and germinal centers
D. Patches of enlarged follicular cells distended with colloid
E. Crowded follicular cells with scalloped colloid
D. Patches of enlarged follicular cells distended with colloid
However, thyroid scintigraphy would show a diffuse uptake of radioactive iodine rather than the focal areas of increased uptake seen here. Furthermore, this patient is missing other classic signs of Graves disease such as ophthalmopathy and pretibial myxedema.
95
A 12-year-old boy presents after a motor vehicle accident with acute left-sided chest pain, dyspnea, hypotension, tachycardia, distended neck veins, tracheal deviation to the right, hyperresonant left chest, and decreased breath sounds.
Emergency needle decompression is indicated. What is the preferred site for needle insertion in a pediatric patient?
A. 2nd intercostal space, midclavicular line
B. 5th intercostal space, midaxillary line
C. 8th intercostal space, posterior axillary line
D. Subxiphoid space
E. 5th intercostal space, midclavicular line
A. 2nd intercostal space, midclavicular line
The 2nd left intercostal space along the midclavicular line is the recommended needle insertion site for emergency decompression of a tension pneumothorax in a child. The patient here is unstable with hypotension and tachycardia, so the pneumothorax should be decompressed as quickly as possible. Since the neurovascular bundle runs below each rib, the upper edge of the rib is the preferred puncture site to help mitigate the risk of excessive bleeding and nerve damage. Emergency needle thoracostomy should be followed by chest tube placement in the 5th intercostal space along the midaxillary line.
According to the Advanced Trauma Life Support (ATLS) guidelines, the 2nd left intercostal space along the midclavicular line is no longer the preferred needle insertion site for emergency decompression of a tension pneumothorax in adults. This location is associated with high failure rates because of increased anterior chest wall thickness. Instead, placing the needle in the 5th left intercostal space along the midaxillary line is preferable.
96
Does rheumatoid arthritis impact the DIP joints?
No! Osteoarthritis DIP and PIP.
97
A 36-year-old woman, gravida 2, para 1, at 30 weeks' gestation comes to the physician for evaluation of increased urinary frequency. She has no history of major medical illness. Physical examination shows no abnormalities. Laboratory studies show an increased serum C-peptide concentration. Ultrasonography shows polyhydramnios and a fetus that is large for gestational age. Which of the following hormones is predominantly responsible for the observed laboratory changes in this patient?
Estrogen
Human placental lactogen
Thyroxine
Human chorionic gonadotropin
Adrenocorticotropic hormone
Progesterone
Human placental lactogen
This patient presents with polyuria, polyhydramnios, a large-for-gestational-age fetus, and elevated maternal C-peptide at 30 weeks’ gestation, which are classic features of gestational diabetes mellitus (GDM).
Key points:
Human placental lactogen (hPL):
Secreted by the syncytiotrophoblast of the placenta.
Peaks in the third trimester.
Causes maternal insulin resistance, ensuring glucose is available for the fetus.
Leads to increased maternal insulin secretion, reflected as elevated C-peptide.
Other hormones:
Hormone Relevance
Estrogen Supports uterine growth and blood flow, minor effect on insulin sensitivity
Progesterone Maintains pregnancy, relaxes smooth muscle, minor metabolic effect
hCG Peaks in first trimester, maintains corpus luteum, not responsible for insulin resistance
Thyroxine Regulates metabolism, not a main driver of gestational hyperglycemia
ACTH Stimulates cortisol, which can induce insulin resistance, but hPL is the predominant hormone in pregnancy-related insulin resistance
Summary:
Maternal hyperglycemia in late pregnancy → hPL-mediated insulin resistance
Fetal effects: Increased glucose → macrosomia, polyhydramnios due to fetal polyuria
Maternal labs: Compensatory hyperinsulinemia → elevated C-peptide
USMLE-style mnemonic:
“hPL = High sugar for the baby” → hPL induces maternal insulin resistance to supply glucose to the fetus.
98
A 36-year-old woman at 30 weeks’ gestation presents with increased urinary frequency. Labs show elevated serum C-peptide, and ultrasound reveals polyhydramnios and a large-for-gestational-age fetus. Which hormone is primarily responsible for the maternal laboratory findings?
A. Estrogen
B. Human placental lactogen
C. Thyroxine
D. Human chorionic gonadotropin
E. Adrenocorticotropic hormone
F. Progesterone
Correct Answer: B. Human placental lactogen ✅
Explanation:
Key features: Polyuria, polyhydramnios, macrosomia, elevated C-peptide → gestational diabetes mellitus.
Human placental lactogen (hPL): Secreted by the placenta, induces maternal insulin resistance and beta-cell hyperplasia, increasing insulin and C-peptide.
Ensures glucose availability for the fetus; maternal hyperglycemia → fetal hyperinsulinemia → macrosomia.
Other hormones (estrogen, progesterone, hCG, thyroxine, ACTH) do not predominantly drive maternal hyperglycemia in late pregnancy.
Mnemonic: “hPL = High sugar for the baby”
Comlex 1
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