What is the management for a 20-year-old patient with elevated Anti-Streptolysin O (ASO) titer, hematuria, fever, and bilateral leg pain?

Management of Post-Streptococcal Glomerulonephritis in a Young Adult

Immediate Diagnosis Confirmation

This 20-year-old patient with elevated ASO titer, hematuria, fever, and bilateral leg pain most likely has acute post-streptococcal glomerulonephritis (APSGN), and management should focus on supportive care with close monitoring, as this is typically a self-limited disease that does not require immunosuppression. 1

The clinical presentation is classic for APSGN:

• Latency period: APSGN typically presents 7-14 days after pharyngeal infection or 14-21 days after skin infection 1
• Elevated ASO titer: Confirms recent streptococcal infection 2, 1
• Hematuria: Cardinal feature of acute glomerulonephritis 1
• Bilateral leg pain: Likely represents edema and fluid overload 3

Essential Diagnostic Workup

Obtain the following laboratory tests immediately:

• Serum complement levels (C3, C4): C3 will be low in APSGN while C4 remains normal, distinguishing it from lupus nephritis 1, 3
• Complete metabolic panel: Assess creatinine, BUN, and electrolytes to evaluate renal function 3
• Urinalysis with microscopy: Quantify proteinuria and hematuria; look for RBC casts which are pathognomonic for glomerulonephritis 1
• Anti-DNase B titer: If ASO is equivocal or to increase diagnostic sensitivity, as combined testing detects up to 98% of streptococcal infections 4
• Blood pressure measurement: Hypertension is common and requires management 1, 5
• Complete blood count: Assess for anemia and infection 3

Supportive Management Strategy

The cornerstone of APSGN management is supportive care, not immunosuppression. 1, 5

Fluid and Electrolyte Management

• Sodium restriction: Limit to 1-2 grams daily to manage edema and hypertension 1
• Fluid restriction: If significant edema or oliguria present 3
• Diuretics: Loop diuretics (furosemide) for symptomatic edema and volume overload 3

Blood Pressure Control

• Target: Maintain BP <130/80 mmHg 1
• First-line agents: ACE inhibitors or calcium channel blockers for hypertension management 6
• Monitor closely: Hypertension can be severe in acute phase 5

Infection Management

• Antibiotics are NOT routinely indicated for APSGN itself, as the glomerulonephritis is an immune-mediated complication occurring after the infection has resolved 1
• However, if there is evidence of ongoing streptococcal infection (persistent fever, positive throat culture), treat with penicillin or amoxicillin per standard protocols 2
• Evaluate for other sources of fever: Blood and urine cultures if fever persists 3

What NOT to Do

Do not initiate immunosuppression with cyclophosphamide and glucocorticoids. 2, 1 This aggressive regimen is reserved for anti-GBM disease, not APSGN. The evidence provided about anti-GBM treatment 2 is not applicable to this post-streptococcal case.

Do not treat empirically without confirming the diagnosis, as the differential includes:

• Lupus nephritis (would have positive ANA, low C3 AND C4) 6
• IgA nephropathy (normal complement levels)
• Anti-GBM disease (requires immediate plasmapheresis if confirmed) 2

Monitoring and Follow-Up

Short-term (First 2-4 weeks):

• Daily weight and blood pressure until stable 1
• Weekly creatinine and urinalysis to track resolution 1
• Repeat C3 level at 8 weeks: Should normalize; persistent hypocomplementemia suggests alternative diagnosis 1, 3

Long-term (Months to Years):

• Urinalysis every 3-6 months for first year to ensure complete resolution 5
• Annual blood pressure checks: Adults have higher risk of persistent hypertension than children 1, 5
• Monitor for chronic kidney disease: Adults may develop CKD in 10-20% of cases, unlike children who almost universally recover completely 1, 5

Prognosis and Patient Counseling

In young adults, APSGN generally has good prognosis but not as uniformly excellent as in children. 1, 5

• Expected timeline: Hematuria may persist for months, but proteinuria and renal function typically improve within weeks 1, 5
• Complete resolution: May take up to 9 years histologically, though clinical resolution occurs much sooner 5
• Risk of progression: Adults have approximately 10-20% risk of developing chronic kidney disease or persistent hypertension, compared to <5% in children 1, 5
• Mortality: Long-term studies show 35% mortality in severe cases presenting on dialysis, but this patient is not in that category 2, 5

When to Consider Renal Biopsy

Renal biopsy is NOT immediately necessary if the clinical picture is classic (elevated ASO, low C3, normal C4, hematuria, recent streptococcal infection). 1

Consider biopsy if:

• Complement levels do not normalize by 8 weeks 1, 3
• Progressive renal dysfunction despite supportive care 5
• Atypical features suggesting alternative diagnosis (very high proteinuria >3.5g/day, low C4, positive ANA) 6
• No improvement in renal function after 4-6 weeks 5

Critical Pitfalls to Avoid

• Do not confuse chronic GAS carrier state with active APSGN: Carriers have positive throat cultures but lack rising antibody titers and are at very low risk for complications 7, 8
• Do not use ASO titers to diagnose acute pharyngitis: ASO reflects past immunologic events, not current infection 2, 4
• Do not forget age-specific reference ranges: Normal ASO levels are higher in school-age children than adults, leading to misinterpretation 2, 4
• Do not initiate aggressive immunosuppression: This is reserved for rapidly progressive glomerulonephritis or anti-GBM disease, not typical APSGN 2, 1