PA8.1-6,PA9.1-2 | Immunopathology & Amyloidosis — Graded Quiz

A 19-year-old woman develops generalised urticaria, stridor, and hypotension within 5 minutes of receiving intramuscular penicillin. Her serum tryptase drawn 2 hours later is 45 µg/L (normal <11.4 µg/L). Which sequence of events correctly describes the effector phase of this reaction?

A 35-year-old man with Goodpasture syndrome has rapidly progressive glomerulonephritis. Renal biopsy immunofluorescence shows a LINEAR pattern of IgG and C3 along the glomerular basement membrane (GBM). His serum complement (C3, C4) levels are NORMAL. In contrast, a patient with post-streptococcal glomerulonephritis (PSGN) has LOW serum complement. Which statement BEST explains this difference?

A 52-year-old woman with long-standing rheumatoid arthritis presents with progressive bilateral leg oedema, frothy urine (3 g/day proteinuria), and hepatomegaly. Renal biopsy shows amorphous, homogeneous, pale eosinophilic deposits in the mesangium and vessel walls that stain apple-green under polarised light after Congo red staining. Which amyloid precursor protein is MOST likely responsible, and what predisposing mechanism is operative?

A 48-year-old man with a 2-year history of multiple myeloma develops macroglossia and carpal tunnel syndrome bilaterally. Echocardiography shows a 'sparkling' myocardial texture and left ventricular wall thickness of 16 mm, but his ECG shows LOW-voltage QRS complexes. Which finding on rectal biopsy would DEFINITIVELY confirm the diagnosis and what is its significance?

A 38-year-old man receives a cadaveric renal transplant. Six months later, he develops rising creatinine, mild proteinuria, and hypertension. Renal biopsy shows interstitial fibrosis, tubular atrophy, intimal thickening of arterial walls, and mononuclear cell infiltrates in the interstitium. There is no fibrinoid necrosis. C4d staining of peritubular capillaries is NEGATIVE. What is the MOST likely diagnosis and the dominant immunological mechanism?

A 29-year-old woman presents with 4 months of joint pain, a photosensitive facial rash, oral ulcers, and pleuritic chest pain. Investigations: ANA positive (1:1280, homogeneous pattern), anti-dsDNA antibody titre elevated, serum C3 = 0.45 g/L (low), C4 = 0.06 g/L (low). Urine shows red cell casts and 3+ proteinuria. Renal biopsy reveals endocapillary proliferation, wire-loop thickening, and 'full-house' immunofluorescence (IgG, IgA, IgM, C3, C1q). What is the WHO/ISN class of nephritis present, and which is the BEST prognostic indicator?

A 36-year-old HIV-positive man (not on ART) presents with fever, weight loss, and drenching night sweats for 6 weeks. Examination reveals cervical and axillary lymphadenopathy and splenomegaly. His CD4 count is 62 cells/µL and viral load is 380,000 copies/mL. Sputum AFB smear is negative. Lymph node biopsy shows effacement of normal architecture by sheets of macrophages with intracellular organisms (PAS positive, non-encapsulated). Serum LDH is markedly elevated. Which pathogen is MOST likely, and at which CD4 count threshold does this opportunistic infection typically emerge?

A contact allergy patch test is performed on a 33-year-old woman suspected of nickel sensitivity. The site shows redness, induration, and vesiculation at 72 hours. Histologically, the dermis contains CD4+ T lymphocytes and macrophages around dermal vessels. The epidermis shows spongiosis. Which sequence of events correctly describes the SENSITISATION phase that occurred weeks earlier on first exposure to the metal?

A 62-year-old man with a history of multiple myeloma (IgG kappa type) presents with a 6-month history of constipation, peripheral oedema, and progressive dyspnoea on exertion. Echocardiography shows concentric left ventricular thickening (18 mm) with a granular 'sparkling' texture; ejection fraction is 50%. His ECG shows generalised low-voltage QRS complexes with a pseudo-infarction pattern in V1-V3. Serum protein electrophoresis shows a monoclonal spike; urine immunofixation is positive for free kappa light chains. Which ONE test would most definitively subtype the amyloid deposit and guide treatment?

A 45-year-old woman develops a serum sickness–like illness 10 days after receiving horse anti-tetanus immunoglobulin. She has fever, urticarial rash, polyarthralgia, and proteinuria. Investigations show: low C3 and C4, elevated ESR, and eosinophilia. Renal biopsy shows granular IgG and C3 deposits in a mesangial and subendothelial pattern. Which pathological process BEST explains her proteinuria?

A 33-year-old HIV-positive man (CD4 count 38 cells/µL, viral load 450,000 copies/mL, not on ART) develops severe headache, neck stiffness, and photophobia over 5 days. Lumbar puncture: opening pressure 340 mmH₂O, CSF is clear, cell count 12 cells/mm³ (predominantly mononuclear), protein 65 mg/dL, glucose 32 mg/dL (simultaneous blood glucose 110 mg/dL). India ink preparation is POSITIVE. Which additional CSF finding would MOST strongly support the diagnosis, and what is the first-line treatment?

A 60-year-old man with a 15-year history of bronchiectasis secondary to recurrent bacterial pneumonias presents with massive proteinuria (6 g/day) and hepatomegaly. His serum albumin is 1.8 g/dL. Renal biopsy shows PAS-negative amorphous deposits in the mesangium and vessel walls that are Congo red positive with apple-green birefringence. Immunohistochemistry of the deposits is NEGATIVE for kappa and lambda light chains but POSITIVE for SAA protein. Which pathophysiological mechanism BEST explains the progression from bronchiectasis to this complication?