Correct Answer: B. Membranous nephropathy
Membranous nephropathy (MN) is the classic diagnosis when a patient presents with nephrotic syndrome (facial puffiness, frothy urine) and the pathognomonic spike and dome pattern is seen on electron microscopy. This pattern represents subepithelial immune complex deposits with projections of the glomerular basement membrane (GBM) between them—a hallmark finding unique to MN. The clinical triad here is crucial: (1) nephrotic syndrome (proteinuria causing frothy urine and edema), (2) microscopic hematuria (indicating glomerular injury), and (3) hypertension (common in MN due to proteinuria and volume expansion). Hepatitis B seropositivity is a well-recognized secondary cause of MN in Indian populations, particularly in endemic regions. In India, HBsAg-associated MN accounts for a significant proportion of secondary MN cases, especially in children and young adults. The light microscopy typically shows thickened GBM ("wire-loop" appearance), and immunofluorescence demonstrates granular IgG and C3 deposits along the capillary wall. MN is the most common cause of nephrotic syndrome in adults globally and the second most common in India after FSGS. The spike and dome pattern on electron microscopy is virtually diagnostic and distinguishes MN from all other glomerulonephropathies.
Why the other options are wrong
A. Minimal change disease — Minimal change disease (MCD) presents with nephrotic syndrome but does NOT cause hematuria—it is characterized by selective proteinuria without RBCs in urine. Electron microscopy shows only foot process effacement, never spike and dome pattern. MCD is the most common cause of nephrotic syndrome in Indian children but rare in adults; the presence of hematuria and spike-dome pattern rules it out completely. C. PSGN-associated disease — Post-streptococcal glomerulonephritis (PSGN) presents with nephritic syndrome (hematuria, hypertension, RBC casts), not nephrotic syndrome. Patients do not typically have frothy urine or facial edema as primary features. Electron microscopy shows 'humps' (subepithelial deposits), not spike and dome. PSGN is acute and self-limited; the chronic presentation here with HBsAg seropositivity does not fit. D. FSGS — Focal segmental glomerulosclerosis (FSGS) does cause nephrotic syndrome and hematuria but the electron microscopy finding is foot process effacement with segmental sclerosis, never spike and dome pattern. FSGS is the most common primary glomerulonephropathy in India but lacks the pathognomonic EM finding. The spike and dome pattern is specific to MN and excludes FSGS.
High-Yield Facts
- Spike and dome pattern on electron microscopy is pathognomonic for membranous nephropathy and represents subepithelial immune complex deposits with GBM projections.
- Hepatitis B seropositivity is a major secondary cause of MN in Indian populations, particularly in endemic regions; HBsAg-associated MN is common in children and young adults.
- Membranous nephropathy is the most common cause of nephrotic syndrome in adults globally and the second most common in India after FSGS.
- Microscopic hematuria in MN indicates glomerular injury; MN can present with both nephrotic and nephritic features, distinguishing it from MCD.
- Light microscopy in MN shows thickened GBM ('wire-loop' appearance); immunofluorescence shows granular IgG and C3 deposits along the capillary wall.
Mnemonics
SPIKE and DOME = MN Subepithelial deposits with Projections of Immune complexes Keeping Epithelium elevated = Distinctive Of Membranous Entity. The EM pattern is unique to MN and is the discriminating finding. MN Secondary Causes (Indian context) HBV (hepatitis B—most common in India), SLE, Malignancy, Drugs (NSAIDs, penicillamine). Remember: HBV is the leading secondary cause in Indian endemic regions.
NBE Trap
NBE may pair nephrotic syndrome with hematuria to lure students toward FSGS (which is the most common primary GN in India), but the spike and dome pattern is pathognomonic for MN and excludes FSGS. The HBsAg history is a red herring unless you know HBV-associated MN is common in India.
Clinical Pearl
In Indian clinical practice, when you see a patient with nephrotic syndrome and HBsAg positivity, always think MN first—especially in endemic regions. The spike and dome pattern on EM is your diagnostic gold standard and should trigger screening for HBV, SLE, and malignancy as secondary causes before labeling it as primary MN.
_Reference: Robbins Ch. 20 (Kidney); Harrison Ch. 279 (Glomerular Diseases); KD Tripathi Ch. 14 (Renal Pathology)_