Platelets

Question 1

Types of platelet granules

Answer 1

α granules: Low electron density, most abundant. Contains PAF4 (heparin neutralizer) and platelet mitogenic factors (such as PDGF) that stimulate endothelial, smooth muscle, and fibroblast proliferation.

γ granules: Large, less dense than delta (dense) granules. Contain cathepsin, acid phosphatase, and a few beta glucosidases.

δ ganules: The delta stands for dense. Electron dense with a “bull’s eye” appearance. Contain serotonin, calcium, ATP, and ADP.

Peroxisomes: Much smaller than the rest. Contain catalase.

Question 2

Pseudothrombocytopenia

Answer 2

Due to the presence of an anti-EDTA antibody

On smear you will see platelet aggregates.

Question 3

Pseudothrombocytosis

Answer 3

Due to the presence of large immune complexes, often in the setting of a cryoglobulin – it is read by the detector as a platelet due to its size.

Smear will look totally normal with respect to platelet count