Extracellular glomerular microparticles in nephrotic syndrome of heroin users

Intracellular and extracellular glomerular microparticles (GMP) have been described in diverse human glomerulopathies. We have recently detected extracellular GMP in two heroin abusers with nephrotic syndrome. Most of the GMP were approximately 100 nm in diameter (range, 56 to 178 nm), and consisted ultrastructurally of an electron-dense central core surrounded by a concentric, lucent area and an electron-dense limiting membrane. Incomplete forms of GMP and residual laminated membranes without a central core were also present. The distribution of extracellular GMP was both intramembranous and subepithelial; they did not resemble virions morphologically. As these GMP have been observed in human glomerulopathies that are etiologically and morphologically varied, they probably represent nonspecific markers of glomerular injury. The prevalence of GMP in the nephrotic syndrome of heroin abusers awaits cumulative experience.