Clinical History:

A 10-year-old caucasian girl was brought by her parents to their family physician. History revealed that the child had a sore throat for about 10 days prior to the office visit. Initial laboratory tests ordered by the family physician revealed an elevated BUN and creatinine. A urinalysis showed hematuria with dysmorphic RBC's. The patient is referred to a nephrologist. The nephrologist, based upon the usual course of this illness, elects to follow the patient. However, two weeks later, the C3 is still decreased.

Images 1.1 and 1.2:

What are the light microscopic findings?

An endocapillary proliferative glomerulonephritis. The glomerulus shows increased cellularity, with many neutrophils present.

Image 1.3:

What does the immunofluorescence staining show for C3 (staining was negative with C1q, IgM, and IgA)? Staining for IgG is +/-.

Immunofluorescence shows a coarse granular pattern of staining along the capillary basement membranes with C3.

Image 1.4:

What does the electron microscopy show?

There are prominent subepithelial "humps" and there are PMN's in the capillary lumens. The findings are most consistent with post- streptococcal glomerulonephritis.

Questions:

1. What tests should be ordered?

Antistreptolysin O (ASO) - elevated; Complement C3 - decreased.

2. What diagnosis is suggested at this point?

Post-streptococcal glomerulonephritis.

3. What is the differential diagnosis?
• post-streptococcal glomerulonephritis
• IgA nephropathy
• membranoproliferative glomerulonephritis (I or II)
• SLE
4. What additional laboratory tests should be ordered?

C3 nephritic factor - negative (tends to rule out MPGN II); ANA - negative (tends to rule out SLE).