Collapsing glomerulopathy.

Collapsing glomerulopathy is a morphologic variant of focal segmental glomerulosclerosis (FSGS) characterized by segmental and global collapse of the glomerular capillaries, marked hypertrophy and hyperplasia of podocytes, and severe tubulointerstitial disease. The cause of this disorder is unknown, but nearly identical pathologic findings are present in idiopathic collapsing glomerulopathy and human immunodeficiency virus (HIV)-associated nephropathy, and collapsing glomerulopathy has been associated with parvovirus B19 infection and treatment with pamidronate. The pathogenesis of collapsing glomerulopathy involves visceral epithelial cell injury leading to cell cycle dysregulation and a proliferative phenotype. Clinically, collapsing glomerulopathy is characterized by black racial predominance, a high incidence of nephrotic syndrome, and rapidly progressive renal failure. Collapsing glomerulopathy also may recur after renal transplantation or present de novo, often leading to loss of the allograft. The optimal treatment for collapsing glomerulopathy is unknown. Treatments may include steroids or cyclosporine in addition to aggressive blood pressure control, angiotensin converting enzyme inhibitors and/or angiotensin II receptor blockers, and lipid lowering agents. The role of other immunosuppressive agents such as mycophenolate mofetil in the treatment of collapsing FSGS remains to be defined. Prospective clinical trials are needed to define optimal therapy of this aggressive form of FSGS.