Representative scanning electron micrographs of resting platelets and platelets activated with HIT serum in the presence of heparin. Resting platelets or platelets incubated with HIT serum in the presence of 0.1 U/mL heparin were fixed with 2% glutaraldehyde and processed for scanning electrom microscopy (A) The morphology of the representative normal resting platelet. Resting platelets were observed to generally maintain a discoid form. (B) The morphology of a representative platelet incubated with HIT serum. These platelets demonstrated several morphologic changes including absence of a discoid form, presence of pseudopodia and presence of microparticles near the end of the pseudopodia (indicated by arrows). Reprinted from Hughes et al48 with permission.