Pneumonia-associated Acute Glomerulonephritis: Rare or Underdiagnosed?

Case 1

A previously healthy, 4-year-old girl was admitted with a two-day history of vomiting, diarrhea, fever and decreased urine output. At admission, she was dehydrated, blood pressure (BP) was 100/60 mmHg (95th percentile 108/70 mmHg), and she had crepitant rales in the upper lobe of the right lung. Lobar pneumonia was confirmed by chest X-ray ([Fig. 1a]). Initial laboratory findings ([Table 1]) revealed acute kidney injury (AKI, serum creatinine level 1.38 mg/dl), hypoalbuminemia (2.9 gr/dl), and hematuria and proteinuria in urine analysis. The day after, her urine became tea-coloured. Ultrasonography (USG) showed hyperechogenic kidneys. Serum complement 3 (C3) was 12.8 mg/dl (N:90–180), complement 4 (C4) was normal, and anti-nuclear antibody (ANA) and anti-double stranded DNA (anti-dsDNA) were negative. There was no history of recent pharyngeal or cutaneous infection. Firstly, fluid resuscitation, allopurinol and ceftriaxone treatments were initiated. The dehydration and AKI improved (serum creatinine level 0.36 mg/dl). During the follow-up, she had peripheral edema, her urine output decreased, and hypertension developed (BP 115/75 mmHg), so fluid restriction was applied, albumin and furosemide were administered. Teicoplanin and clindamycin were added because of persistent fever after the 3rd day of initial treatment and increased pneumonic infiltration. Macroscopic hematuria resolved on the 5^th day of the antibiotics. Pneumonia treatment was completed, and she was discharged 3 weeks after admission with 0.30 mg/dl creatinine, 4.2 g/dl albumin and ongoing proteinuria (spot urine protein-to-creatinine ratio [UPCR] 0.72 mg/mg) and microscopic hematuria, and normal BP without antihypertensives. At the follow-up visit after 2 weeks, the C3 level was normal (90 mg/dl), spot UPCR was 0.25 mg/mg, and microscopic hematuria (22 red blood cells/hpf) continued. After 3 months, proteinuria and microscopic hematuria disappeared, and renal hyperechogenicity on USG also resolved.

Fig. 1 Chest X-ray images of Case 1 (a) and Case 2 (b).

Table 1 Clinical and laboratory characteristics of the patients at the time of admission

Clinical and laboratory features	Case 1	Case 2
Age (year)/gender	4/female	10/male
Blood pressure, at onset (mmHg)	100/60 (95th percentile 108/70 mmHg)	140/95 (95th percentile 116/78 mmHg)
Serum creatinine (mg/dl)	1.38	0.53
eGFR (ml/min/1.73 m2, modified Schwartz)	29.3	102.8
BUN (mg/dl)	61	20
Uric acid (mg/dl)	17	5.2
Albumin (gr/dl)	3.0	3.6
Hemoglobin (g/dl)	9.6	9.0
WBC (x103/ μl)	13.67	15.15
Platelets (x103/μl)	289	412
Sedimentation rate (mm/hour)	NA	63
CRP (mg/dl, N:0–0.5)	33	<0.31
Urine red blood cell (cells/hpf)	83	153
Urine leucocyte (cells/hpf)	30	2
Urine protein-creatinine ratio (mg/mg)	2.6	1.8
Urine culture	negative	negative
Throat culture	NA	negative for GAS
Blood culture	negative	NA
ASO (IU/ml, N:<200)	NA	394
Complement 3 (mg/dl, N:90–180)	12.8	18.7
Complement 4 (mg/dl, N:10–40)	14.6	12.3
ANA	negative	negative
Anti-dsDNA	negative	negative

ANA, antinuclear antibody; anti-dsDNA, anti-double stranded DNA; ASO, anti-streptolysin O; BUN, blood urea nitrogen; CRP, C-reactive protein; eGFR, estimated glomerular filtration rate; GAS, group A streptococcus; hpf, high-power field; N, normal; NA, not available; WBC, white blood cells.

Publication History

Article published online:
21 August 2025