A child presented to the hospital with cola-colored urine, hypertension, and puffiness of eyes. Laboratory investigations were done, and creatinine was 2.5 mg/dL. Treatment was started, and despite treatment, the patient did not improve for the next 3 weeks. The creatinine value increased to 4.5 mg/dL. Which among the following electron microscopic findings will be seen in this patient?

Correct Answer: A. Subepithelial deposits

This clinical presentation—cola-colored urine, hypertension, periorbital edema, and progressive renal dysfunction (creatinine rising from 2.5 to 4.5 mg/dL over 3 weeks despite treatment)—is pathognomonic for post-streptococcal glomerulonephritis (PSGN), the most common acute glomerulonephritis in Indian pediatric practice. The key discriminator is the subepithelial "hump" deposits seen on electron microscopy, which are virtually diagnostic of PSGN. These humps represent immune complexes (IgG, IgM, C3) deposited between the glomerular basement membrane and the podocytes. On light microscopy, this manifests as diffuse proliferative glomerulonephritis with endocapillary proliferation. The progressive rise in creatinine despite treatment reflects the acute phase of the disease; however, PSGN typically resolves spontaneously over 6–12 weeks in children, though some may develop chronic kidney disease if severely affected. The electron microscopic finding of subepithelial deposits (humps) is the gold standard for confirming PSGN and distinguishing it from other causes of acute nephritic syndrome such as IgA nephropathy or lupus nephritis.

Why the other options are wrong

B. Mesangial deposits — Mesangial deposits are characteristic of IgA nephropathy (most common primary glomerulonephritis worldwide, but presents with hematuria ± proteinuria, NOT acute nephritic syndrome with hypertension and edema). They are also seen in lupus nephritis (Class III/IV) and other secondary glomerulonephritides, but PSGN shows subepithelial humps, not mesangial predominance. This is an NBE trap for students who confuse IgA nephropathy with PSGN. C. Crescent formation — Crescent formation indicates rapidly progressive glomerulonephritis (RPGN), seen in ANCA-associated vasculitis, anti-GBM disease, or immune complex RPGN. While this patient has progressive renal dysfunction, the clinical triad of cola-colored urine + hypertension + edema is classic for PSGN, which is proliferative, NOT crescentic. Crescents would suggest a more aggressive vasculitic process, which is rare in post-streptococcal disease in children. D. Subendothelial deposits — Subendothelial deposits are the hallmark of lupus nephritis (especially Class III/IV membranoproliferative pattern). While lupus can present with hematuria and hypertension, the clinical context here—acute onset after streptococcal infection, cola-colored urine, and lack of systemic lupus features—points to PSGN. Subendothelial deposits would be found in immune complex disease with endocapillary involvement, not the exudative proliferation of PSGN.

High-Yield Facts

Mnemonics

PSGN EM Findings: HUMP Hump deposits (subepithelial), Under podocytes, Membrane-based, Post-streptococcal. Use this to recall that PSGN = subepithelial humps, not mesangial or subendothelial. Acute Nephritic Syndrome: CHOP Cola urine, Hypertension, Oedema (periorbital), Proteinuria. Helps recall the classic tetrad; PSGN is the most common cause in Indian children.

NBE Trap

NBE pairs progressive renal dysfunction (creatinine rise) with RPGN features (crescents) to lure students away from PSGN, which typically has a benign course in children. The key is recognizing that the clinical presentation (acute nephritic syndrome post-streptococcal infection) overrides the rising creatinine—PSGN can have transient worsening but resolves spontaneously, whereas crescents indicate a different pathology.

Clinical Pearl

In Indian pediatric practice, PSGN is the most common cause of acute nephritic syndrome in children aged 5–12 years, often following impetigo or pharyngitis. The presence of subepithelial humps on EM is so characteristic that a renal biopsy showing this finding essentially confirms PSGN and reassures families that the prognosis is generally excellent despite initial severe presentation.

_Reference: Robbins Ch. 20 (Kidney); Harrison Ch. 279 (Glomerular Diseases); OP Ghai Pediatrics Ch. 12 (Renal System)_