Acute Kidney Injury Management, Pauci-Immune Glomerulonephritis (GN), Glomerulonephritis: Causes, Di

Описание: A 4-year-old boy presents with dark urine, pallor, rapid breathing, and neurological findings, following a recent history of upper airway symptoms and pulmonary changes. Lab findings reveal anemia, kidney injury, and abnormal urinalysis, while imaging and bronchoscopy point to diffuse lung involvement. What diagnostic strategies help integrate his multisystem findings? Which clinical features are most important in narrowing the differential for pulmonary-renal syndrome in children?

VIDEO INFO
Category: Acute Kidney Injury Management, Pauci-Immune Glomerulonephritis (GN), Glomerulonephritis: Causes, Diagnosis, and Management, Nephrology: Kidney Disease Diagnosis and Management
Difficulty: Hard - Advanced level - Challenges experienced practitioners
Question Type: Differential Comprehensive
Case Type: Complicated Condition

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QUESTION
A 4-year-old boy is brought to the pediatric emergency department for 2 days of dark urine, pallor, and rapid breathing. He was treated for giardiasis 6 months ago. At age 3 he was evaluated for paroxysmal episodes of sweating and pallor; outpatient imaging suggested an adrenal lesion, but serial evaluations since then have not confirmed catecholamine excess, and he has needed no therapy....

OPTIONS
A. Granulomatosis with polyangiitis (PR3-ANCA-associated pauci-immune small-vessel vasculitis) presenting with pulmonary-renal syndrome and mononeuritis multiplex.
B. Microscopic polyangiitis (MPO-ANCA vasculitis) with pulmonary-renal syndrome despite PR3-positive and MPO-negative serology.
C. Anti-glomerular basement membrane antibody disease (Goodpasture disease) causing pulmonary-renal syndrome with immune-complex deposition on kidney biopsy.
D. Infection-related glomerulonephritis with concurrent community-acquired pneumonia producing hematuria and diffuse alveolar hemorrhage.

CORRECT ANSWER
A. Granulomatosis with polyangiitis (PR3-ANCA-associated pauci-immune small-vessel vasculitis) presenting with pulmonary-renal syndrome and mononeuritis multiplex.

EXPLANATION
Basic teaching point: In children, granulomatosis with polyangiitis can present with pulmonary-renal syndrome featuring PR3-ANCA positivity, ENT disease, neuropathy, diffuse alveolar hemorrhage, and pauci-immune crescentic GN on biopsy. "Granulomatosis with polyangiitis (PR3-ANCA-associated pauci-immune small-vessel vasculitis) presenting with pulmonary-renal syndrome and mononeuritis multiplex." best integrates this child s constellation: c-ANCA pattern with strong PR3 positivity, ENT crusting/sinus tenderness, hypoxemia with increasingly bloody BAL and hemosiderin-laden macrophages, and kidney biopsy showing crescents in greater than 50% of glomeruli with pauci-immune immunofluorescence-plus asymmetric peroneal neuropathy.

"Microscopic polyangiitis (MPO-ANCA vasculitis) with pulmonary-renal syndrome despite PR3-positive and MPO-negative serology." conflicts with the specific serology and ENT/neuropathy features more typical of GPA. "Anti-glomerular basement membrane antibody disease (Goodpasture disease) causing pulmonary-renal syndrome with immune-complex deposition on kidney biopsy." is inconsistent because anti-GBM is negative and the biopsy is pauci-immune (anti-GBM shows linear IgG, not pauci-immune)....


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