Chapter review
Bring the chapter together
Start with the case synthesis, answered in 3 separate parts, then work through mixed case-based questions. Every answer explains the clue that matters and why the closest alternative fails.
Case synthesis
Bringing it together: one disease, three mechanisms
A 26-year-old woman has a malar rash, painful hands and ankle edema. Her urine shows red-cell casts and protein; serum C3 and C4 are low; anti-dsDNA is strongly positive; kidney biopsy shows granular IgG, IgM, C1q and C3 in the capillary walls. Her hemoglobin is 8.5 g/dL with spherocytes and a positive direct Coombs test (IgG). Last year she had a deep-vein thrombosis, and a syphilis screen was positive although a treponemal test was negative.
1. Trigger
Why is she making antibodies against her own nuclei?
2. Mechanism in the kidney
Which mechanism is injuring her glomeruli, and which clues prove it?
3. Mechanism in the blood, and what it decides
Which mechanisms explain her anemia and her earlier thrombosis, and what does that change?
Mixed case review
Morphology, mechanism and application. Some items need two sections at once.
- Q1Rheumatoid arthritis as type III (source note)Connects 3.3 + 3.5L3 p.20, 23Ch. III cases p.12
A 36-year-old woman has had fatigue for several months and stiffness in both hands that is worst in the morning and eases after she soaks them in a warm bath. She had an acute throat infection 7 weeks ago. She has a low-grade fever, and subcutaneous nodules are palpable along both forearms.
Which type of hypersensitivity reaction is causing her arthritis?
- Q2Immune-complex GN in an SLE-like caseConnects 3.3 + 3.5L3 p.23, 36–37Ch. III cases p.6
A 38-year-old woman has periorbital edema and throbbing headaches. She has pale conjunctivae and several sharply demarcated raised skin lesions on her forearms. Bleeding time is prolonged and ESR is 54 mm/h. Urinalysis shows 3+ hematuria; a renal biopsy shows hypercellular glomeruli with subepithelial 'humps' on electron microscopy.
Which best explains the pathogenesis of her glomerulonephritis?
- Q3Skin-prick test: IgEConnects 3.2 + 3.3L3 p.19Midterm sim. p.8
A 20-year-old woman with asthma and allergies undergoes skin testing to identify allergens in her environment.
A positive skin reaction to ragweed would be mediated by which immunoglobulin class?
- Q4Anti-D: passive immunity preventing type II HDNConnects 3.1 + 3.3L3 p.4, 20, 22
An Rh(D)-negative woman delivers her first Rh(D)-positive baby. Her indirect Coombs test was negative throughout pregnancy. She receives anti-D immune globulin within 72 hours of delivery.
Which statement best explains why?
- Q5HIV bystander death by pyroptosisConnects 3.1 + 3.7L3 p.5, 49Ref.
In lymph nodes of untreated HIV patients, most dying CD4 T cells are resting cells that contain incomplete reverse transcripts and make no viral proteins.
Which mechanism most likely kills these cells?
- Q6Transfusion-associated GVHD in DiGeorgeConnects 3.4 + 3.6L3 p.32, 45
A 4-week-old boy with truncus arteriosus and neonatal hypocalcemia has heart surgery and receives non-irradiated red cells. Two weeks later he has a widespread rash, diarrhea, jaundice and falling blood counts.
What is the most likely explanation?
- Q7Early complement deficiency and SLEConnects 3.5 + 3.7L3 p.36, 54
A 7-year-old girl has a photosensitive facial rash, arthritis and glomerulonephritis. ANA is positive and C1q is undetectable.
Why does lacking C1q predispose to lupus?
- Q8Inflammasome → SAA → AA amyloidConnects 3.1 + 3.7L3 p.5L1 p.47
A 30-year-old man has had attacks of fever with abdominal and chest pain lasting 1–3 days since childhood; his sister has the same attacks. He has never been treated. He now has heavy proteinuria and edema, and a renal biopsy shows Congo-red–positive deposits.
Which protein is most likely deposited, and why?
- Q9Ataxia–telangiectasia: ATM, AFP, lymphomaConnects 3.6 + 7.4L3 p.46
A 6-year-old boy has been unsteady since he started walking, has telangiectasias on his conjunctivae and ears, and has had recurrent sinus and lung infections. IgA is very low.
Which statement is correct?
- Q10Hyperacute rejection = transfusion reaction mechanismConnects 3.3 + 3.4L3 p.20, 29–30
A kidney from a group A donor is transplanted into a group O recipient by mistake and becomes cyanotic within minutes; separately, a group O patient transfused with group A red cells develops intravascular hemolysis within hours.
Which mechanism do the two events share?
- Q11Anergy: PPD in advanced HIVConnects 3.2 + 3.3 + 3.7L3 p.26, 51
A 35-year-old man with untreated HIV (CD4 count 60/mm³) has fever, night sweats and miliary nodules on chest x-ray; sputum grows M. tuberculosis. A tuberculin skin test shows no induration at 72 hours.
Why is the skin test negative?
- Q12Wiskott–Aldrich: small plateletsConnects 3.3 + 3.6L3 p.20, 46
A 2-year-old boy has eczema, recurrent otitis and episodes of petechiae and bloody stools. Platelet count is 40,000/µL, and the platelets are about half the normal size.
What is the most likely diagnosis?
- Q13β₂-microglobulin amyloidConnects 3.2 + 3.7L3 p.12–13L1 p.47
A 58-year-old man has been on hemodialysis for 12 years. He has bilateral carpal tunnel syndrome and shoulder pain; synovial biopsy shows Congo-red–positive deposits.
The precursor of these deposits normally:
- Q14Myasthenia gravis: blocking antibodyConnects 3.3 + 3.5L3 p.20, 22
A 28-year-old woman has drooping eyelids and double vision that worsen as the day goes on. Antibodies against the acetylcholine receptor are present, and CT shows an enlarged thymus.
Which best describes the mechanism of her weakness?
- Q15Costimulation, anergy and checkpoint colitisConnects 3.2 + 3.5L3 p.11, 34Ref.
A 60-year-old man with metastatic melanoma is treated with an antibody that blocks CTLA-4. Six weeks later he has severe diarrhea, and colonoscopy shows colitis heavily infiltrated by T cells.
What best explains the colitis?
- Q16Rheumatic fever vs PSGNConnects 3.3 + 3.5L3 p.20, 23, 34
Two children have group A streptococcal pharyngitis. Three weeks later, one has fever, migratory arthritis of large joints and a new heart murmur; the other has cola-colored urine, edema and a low C3.
Which statement correctly contrasts the two complications?
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