Focal Segmental Glomerulosclerosis and Parvovirus B19

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Focal segmental glomerulosclerosis (FSGS) is a glomerular disease with a characteristic pathologic presentation that includes segmental scarring involving some but not all glomeruli. On immunofluorescence, deposits of immunoglobulin (Ig) M and C3 may be found in the areas of segmental scarring. Electron microscopy typically demonstrates diffuse epithelial cell foot process effacement and focal areas of retraction of glomerular basement membrane with collapse of the involved tuft (1). Due to the focal nature of the process, it is sometimes challenging to recognize this lesion in the biopsy specimen. Accordingly, special attention needs to be directed at the corticomedullary regions of the kidney where FSGS is more likely to be found. Otherwise, an errant diagnosis of minimal change disease could be made. Once underlying causes of this particular glomerular presentation are ruled out (such as obesity, sleep apnea, heroin abuse, reflux nephropathy, and HIV), one is left with a diagnosis of primary or idiopathic FSGS. It is important to identify patients who present with nephrotic-range proteinuria and have FSGS because early treatment of these patients may alter the course of the disease and prevent relentless progression to terminal renal failure (2). The collapsing form of FSGS, which occurs more commonly in African American patients than in Caucasians, carries a particularly poor prognosis with respect to renal survival (3). This variant is morphologically similar to the glomerular lesion often associated with HIV infection. However, the term idiopathic collapsing glomerulopathy is reserved for patients who are HIV negative. Collapsing glomerulopathy has been associated with non–HIV-related pathologies. These include associations with medications like pamidronate and interferon-alfa and with viral infections like parvovirus B19, cytomegalovirus, and hepatitis C (4, 5). Rarely, multiple myeloma has been associated with this lesion (6, 7). A case of collapsing FSGS in a patient with parvovirus B19 infection is presented with review of the known literature.