Glomerular and systemic renal disease
Distinguish a clinical syndrome from a biopsy pattern and from its cause. Nephrotic-range protein loss, edema and low serum albumin suggest a nephrotic presentation, while dysmorphic erythrocytes and red-cell casts support glomerular bleeding. Either syndrome can coexist with reduced filtration. Heavy proteinuria alone does not identify a single histologic lesion, and a child with a typical first presentation does not automatically require an invasive biopsy before every treatment decision.
Read renal pathology across light microscopy, immunofluorescence and electron microscopy. Minimal-change disease can show little light-microscopic abnormality with extensive podocyte foot-process change. Focal segmental sclerosis describes a pattern with primary, adaptive and genetic causes; the pattern does not automatically justify the same immunosuppression for every patient. Membranous disease may involve circulating antibodies to a podocyte antigen, but investigation for associated conditions remains relevant. A positive marker supports a coherent diagnosis rather than erasing clinical context.
Immune-deposit location helps connect morphology to mechanisms. Linear immunoglobulin staining supports anti-basement-membrane disease in the appropriate presentation. Granular deposits suggest immune-complex processes. Pauci-immune necrotizing disease has scant immunoglobulin staining and may accompany ANCA-associated vasculitis. Complement-dominant disease requires evaluation of alternative-pathway abnormalities and associated conditions; a membranoproliferative appearance is not itself one unique etiology.
Lupus nephritis classification integrates the extent and character of lesions. Treatment decisions additionally depend on activity, chronic damage, filtration, pregnancy intentions, comorbidity and patient preferences. Contemporary treatment options evolve, so an older recognized induction regimen should not be misrepresented as the only modern strategy. Likewise, plasma exchange is not an automatic treatment for every ANCA-positive renal presentation; anti-basement-membrane disease and selected severe situations require their own assessments.
Systemic clues can be decisive. Amyloid deposition, a monoclonal protein, thrombotic microangiopathy or a compatible infection can change the differential and required investigations. A small circulating monoclonal clone can still cause clinically important renal injury. Severe ADAMTS13 deficiency supports thrombotic thrombocytopenic purpura, but urgent treatment decisions may precede the result when suspicion is high. Finally, follow the trajectory: a biopsy label without assessment of progression, complications and response is an incomplete account of the patient.