Use of the electron microscope for diagnosis of platelet disorders.

The electron microscope is generally regarded as a sophisticated instrument used almost exclusively for basic research. However, ultrastructural methods can be just as valuable for the clinical diagnosis of inherited platelet disorders, as for more fundamental studies. This report describes several instances in which electron microscopy has been critical for identifying and characterizing genetic problems. For example, platelet storage pool deficiency (SPD) is due to a marked decrease or absence of the organelles storing adenine nucleotides, serotonin, and calcium destined for secretion during the platelet release reaction. The organelles are referred to as dense bodies because they are inherently electron opaque. As a result, platelet SPD is more rapidly and reliably diagnosed in the electron microscope than by any other technique. Giant platelet disorders have presented a bewildering array. The electron microscope has made it possible to separate the various types into distinct conditions based on the nature of platelet structural defects and inclusions found in leukocytes. Immunogold and cytochemical techniques have expanded the horizon of electron microscopy in the evaluation of platelet disorders and have assured its continued use for this purpose in the future.