Assessment of the Stability of von Willebrand Profile Clotting Factors and Platelet Dense Granule Testing Following Air Transport

Platelet Storage Pool Deficiency and Elevated Inflammatory Biomarkers Are Prevalent in Postural Orthostatic Tachycardia Syndrome

A significant number of postural orthostatic tachycardia syndrome (POTS) patients have platelet delta granule storage pool deficiency (δ-SPD). The etiology of POTS is unknown but a number of laboratories, including ours, have reported elevations of G-protein-coupled adrenergic receptor and muscarinic acetylcholine receptor autoantibodies in POTS patients, detected by a variety of techniques, suggesting that the disorder is an autoimmune condition. Thus, it could also be considered an inflammatory disease. In a pilot study, we investigated a limited number of platelet-related cytokines and chemokines and discovered many that were elevated. This case−control study validates our pilot study results that POTS patients have an activated innate immune system. Plasma of 35 POTS patients and 35 patients with unexplained bleeding symptoms and categorized as “non-POTS” subjects was analyzed by multiplex flow cytometry to quantify 16 different innate immune system cytokines and chemokines. Electron microscopy was used to quantify platelet dense granules. Ten of 16 biomarkers of inflammation were elevated in plasma from POTS patients compared to non-POTS subjects, with most of the differences extremely significant, with p values < 0.0001. Of particular interest were elevations of IL-1β and IL-18 and decreased or normal levels of type 1 interferons in POTS patients, suggesting that the etiology of POTS might be autoinflammatory. All POTS patients had δ-SPD. With a growing body of evidence that POTS is an autoimmune disease and having elevations of the innate immune system, our results suggest a potential T-cell-mediated autoimmunity in POTS characteristic of a mixed-pattern inflammatory disease similar to rheumatoid arthritis.

A Morphometric Analysis of Platelet Dense Granules of Patients with Unexplained Bleeding: A New Entity of Delta-Microgranular Storage Pool Deficiency

One thousand and eighty patients, having prolonged bleeding times, frequent epistaxis, menorrhagia or easy bruising or other bleeding manifestations, and excluding those with von Willebrand's disease, were evaluated for platelet dense granule deficiency. The mean diameter of platelet dense granules was determined for all patients using image analysis. Four hundred and ninety-nine had "classic" dense (delta) granule storage pool deficiency (δ-SPD). Five hundred and eighty-one individuals (53.8%) were found to have a normal mean number of dense granules, but for some of these patients, the dense granules were smaller than for the controls. Of the patients having a normal number of dense granules, 165 (28.4%) were found to have significantly smaller granules than the platelets obtained from the control subjects. Their average granule diameter was 123.35 ± 0.86 nm, that is more than three standard deviations below the mean of the control data. Total δ-granule storage pool volumes (TDGV)/platelet were calculated using these measurements. Individuals with δ-SPD had half the number of granules (2.25 ± 0.04 DG/PL) and storage pool volume (3.88 ± 1.06 × 106 nm3) when compared to our control data (4.64 ± 0.11 DG/PL; 10.79 × 106 nm3 ± 0.42). Individuals having a bleeding history but a normal average of small dense granules had a calculated storage pool volume statistically different than controls and essentially the same storage pool volume as patients with δ-SPD. We have identified a sub-classification of δ-SPD that we have defined as micro-granular storage pool deficiency (δ-MGSPD).