To the Editor.
—The article by Muehrcke et al "The Clinical Value of Electron Microscopy in Renal Disease" (Arch Intern Med124:170-176, 1969) deserves a comment because light microscopy can replace electron microscopy only in part.From their observations on 179 renal biopsy specimens the authors concluded that "electron microscopy need not be performed as a routine procedure," because it contributed significantly in only 6% of their cases to the diagnosis. It may be questioned whether the application of routine electron microscopy should be judged by its immediate diagnostic value. It appears to me that our knowledge of structural changes in the kidney, as seen by electron microscopy, is far from being complete.It is true that electron microscopic studies of idiopathic lipoid (non-membranous) nephrosis and acute glomerulonephritis are only occasionally of value for diagnosis. But electron microscopy as a tool for identifying disease entitie, for instance in the