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October 25, 2017

Cryoglobulinemic Deposits by EM

Electron microscopy can be helpful in the diagnosis of cryoglobulinemic glomerulonephritis. This renal biopsy (Fig. 1) shows a membranoproliferative pattern glomerulonephritis in which the extent of endocapillary hypercellularity and glomerular capillary double contour formation is nicely highlighted with a Jones silver stain. The patient had a long history of hepatitis C infection, and you can clearly see intraluminal hyaline thrombi – “pseudothrombi” – in some capillary lumens, which are a helpful clue in diagnosing cryoglobulinemic glomerulonephritis. Some cases of cryoglobulinemic glomerulonephritis show electron dense deposits with organized substructure (Fig. 2), including tubular, fibrillar, crystalloid, or even fingerprint-like patterns. Early work on the ultrastructural features of such deposits was performed on transmission electron microscopes much like the one in this picture taken circa 1960 (courtesy of the CDC) (Fig. 3).


Dr. Hogan
This 1960 photograph depicted a laboratory technician who was seated at a transmission electron microscope (TEM), as she was analyzing the ultrastructural details of a laboratory specimen.

A TEM works much like a light microscope, for rather than implementing light waves as a means to illuminate the ultrastructural details of a slide specimen, electrons, which travel at a much lower wavelength, and therefore, enable the observer to see these details under a resolution many times greater than when using light. Electromagnets are used as the lenses for this device rather than glass lenses, focusing the beams of electrons through the specimen, which finally hit a fluorescent screen that scintillates when the electrons hit its sensitive surface.