The variant Gly109Glu in β1-tubulin alters platelet ultrastructure. Electron microscopy of platelets from 2 homozygous and a heterozygous carrier of the β1-tubulin p.Gly109Glu and from 2 healthy controls. In contrast to control platelets, most platelets from homozygous p.Gly109Glu carriers were round and large and showed a slightly hypertrophic open canalicular system and an irregular membrane demarcation system (white arrows and asterisks, respectively). Magnification for each image is shown (8000-15 000×). Images were acquired in a Philips/FEITecnai12 transmission electron microscope.