Diagnosis: Post-Streptococcal Glomerulonephritis (PSGN)
This patient has post-streptococcal glomerulonephritis (PSGN), and the primary management is supportive care with close monitoring, as immunosuppressive therapy is not indicated for typical PSGN. 1, 2, 3
Clinical Reasoning
The constellation of findings strongly points to PSGN:
- Facial edema with albuminuria (2+) indicates glomerular injury with fluid retention 3
- Hematuria with dysmorphic RBCs confirms glomerular origin of bleeding 4, 5
- Elevated ASO titer provides serologic evidence of recent streptococcal infection 1, 2, 3
- Normal C3 is atypical but does not exclude PSGN, as complement levels can normalize by presentation or remain normal in some cases 3
- Normal blood pressure is reassuring and indicates less severe disease 1, 3
The normal C3 deserves special attention. While classically PSGN presents with low C3, this patient may have presented later in the disease course when complement has normalized, or represents a variant presentation. 3 The elevated ASO with the nephritic picture (hematuria with dysmorphic RBCs) makes PSGN the most likely diagnosis despite normal complement. 2
Differential Considerations
Rule out IgA nephropathy (IgAN): IgAN can present similarly with hematuria, proteinuria, and elevated ASO (during concurrent infection), but typically has normal complement and lacks the acute nephritic presentation with edema. 6 A kidney biopsy would show IgA-dominant immunofluorescence rather than the C3-dominant pattern of PSGN.
Rule out C3 glomerulopathy: The normal C3 makes this less likely, though C3 glomerulonephritis can occasionally present with elevated ASO. 7, 8 However, C3 glomerulopathy typically shows persistent hypocomplementemia and requires biopsy for definitive diagnosis.
Rule out ANCA-associated vasculitis: The normal blood pressure and absence of systemic symptoms make this unlikely. 4, 5 ANCA testing should be performed if there are pulmonary symptoms, sinusitis, or rapidly progressive renal failure.
Management Strategy
Immediate Actions
Supportive care is the cornerstone of PSGN management: 6, 1, 2, 3
- Sodium restriction to 2 grams daily to manage edema 6
- Diuretics (loop diuretics preferred) for persistent edema despite sodium restriction 6
- Monitor fluid balance carefully to avoid volume depletion 6
- Blood pressure control if hypertension develops, though currently normal 6
Monitoring Parameters
Serial laboratory assessment is essential: 3
- Renal function (creatinine, GFR) every 2-3 days initially to detect deterioration 3
- Urinalysis weekly to monitor hematuria and proteinuria resolution 1
- Repeat C3 level in 1-2 weeks; persistent low C3 beyond 8 weeks suggests alternative diagnosis 3
- Blood pressure daily until stable 6
When to Consider Biopsy
Kidney biopsy is indicated if: 6
- Renal function deteriorates (rising creatinine, declining GFR) 6
- Proteinuria persists beyond 6 months 1
- Hematuria persists beyond 12-18 months 1
- C3 remains low beyond 8 weeks 3
- Clinical course is atypical or severe 6
Immunosuppression: Not Indicated
Do not use corticosteroids or other immunosuppressive agents for typical PSGN. 6, 1, 2 PSGN is a self-limited disease with excellent prognosis, particularly when presenting without severe renal impairment or hypertension. 1, 3 Immunosuppression is reserved for proven chronic glomerulonephritis patterns (like IgAN or crescentic GN) confirmed by biopsy, not for acute post-infectious GN. 6
Renin-Angiotensin System Blockade
ACE inhibitors or ARBs are not routinely indicated in PSGN unless hypertension develops or proteinuria persists beyond the acute phase. 6 Since blood pressure is currently normal and this is acute disease, hold off on RAS inhibition initially. If proteinuria exceeds 1 g/day at 3-6 months follow-up, consider ACE-I/ARB therapy. 6
Prognosis
The prognosis for PSGN is excellent, especially in this patient with normal blood pressure and no severe renal impairment. 1, 3 Most patients achieve complete clinical recovery within weeks to months. 1, 2 Histological resolution may take up to 9 years, but clinical normalization of renal function typically occurs much earlier. 1 Children and young adults have particularly favorable outcomes. 3
Critical Pitfalls to Avoid
Do not delay evaluation if renal function worsens: Rapidly progressive glomerulonephritis (RPGN) can mimic PSGN initially but requires urgent biopsy and immunosuppression. 6, 5 If creatinine rises significantly over days, proceed immediately to biopsy without waiting for "typical" PSGN resolution.
Do not assume all post-streptococcal presentations are benign PSGN: Rare cases can develop crescentic transformation requiring aggressive therapy. 6 The normal blood pressure and modest proteinuria (2+) in this case are reassuring, but vigilance is required.
Do not stop monitoring prematurely: Even with clinical improvement, follow urinalysis for 12-18 months to ensure complete resolution. 1 Persistent abnormalities warrant nephrology referral and possible biopsy. 6