Complex glomerular pathology of thrombotic microangiopathy and focal segmental glomerulosclerosis forms tumor-like mass in a renal transplant donor with severe renovascular hypertension

Abstract

The pathogenesis of glomerular hypertension-mediated FSGS and its histological variations in humans remains unknown. A 47-year-old man developed nephrotic syndrome, renal dysfunction, and malignant hypertension 2 years after donating a kidney to his son. The donor’s remnant kidney developed renal mass at an upper pole which was fed by an aberrant artery that branched from the root of the renal artery. Furthermore, the main non-aberrant renal artery demonstrated severe stenosis that caused renovascular hypertension, resulting in malignant hypertension. Upon radiological examinations, a tumorous mass was detected. Because of progressive renal dysfunction, nephrectomy was performed. The kidney revealed a diffuse distribution of complex FSGS lesions, i.e., a random combination of cellular/collapsing FSGS and glomerular thrombotic microangiopathy, confined to the renal mass, whereas such lesions were absent in the non-mass portion. This indicated that severe glomerular hypertension alone caused FSGS with TMA features. Heterogeneous FSGS lesions let us surmise that glomerular hypertension promoted simultaneous damages in endothelial cells and podocytes, which synergistically progressed to glomerulosclerosis. This unique case uncovers causal relationships between unusual glomerular hypertension and severe forms of FSGS that was possibly caused by the disruption of homeostasis sustained by podocytes and endothelial cells.