Case 6Helmut Hopfer, University Hospital Basel, Switzerland

morphological features

• increased number of endocapillary leukocytes• endothelial swelling• dilatation of capillary loops• occlusion or near occlusion of capillary lumina with cells

usually a focal and segmental lesion!

EM differential diagnosis

transplant glomerulitis endocapillary glomerulonephritis (intravascular lymphoma)

• recognizing a pattern:1. increased number of endocapillary leukocytes2. endothelial swelling3. dilatation of capillary loops4. occlusion or near occlusion of capillary lumina with cells

• counting mononuclear cells (arbitrary cut-off)

→ no clear distinction between cell types by light microscopy!→ immunohistochemistry, definition of cut-off by ROC

Example: endocapillary immune-complex GN

transplant glomerulitis: definition

CD5 CD20 CD68 ERG

counting cells will not tell youanything about the pathogenesis

glomerular rejection: pathogenesis

antibodies & complement↓

endothelial cell damage

lytic sublytic

necrotic procoagulant proinflammatory proliferative / reparative

1.

2.3.

1.

2.

3.

antibodies & complement↓

endothelial cell damage

lytic sublytic

proliferative / reparativeproinflammatoryprocoagulant

necrotic

discussion & conclusions

• Why are the leukocytes there?

• What are the monocytes / macrophages doing there?

• What are the lymphocytes doing there?

→ monocytes exert an early endocapillary reparative function on the endothelial cells

case presentation

Clinical history:39 year old male. Renal transplantation (TR) in 2005 due to hypertension. Malcompliance with immunosuppresion → two episodes of interstitial cellular rejection.Diagnostic biopsy (BX) 40 months after TR, rise in creatinine and newly diagnosed proteinuria.

Diagnosis:Transplant glomerulitis (by EM), severe diffuse interstitial cellular rejection, C4d negative. Focal IFTA (10-20%).

Follow up:Dialysis dependence 7 months later. BX with mixed T cell- and antibody-mediated rejection, C4d positive.