Postural orthostatic tachycardia syndrome in post-COVID-19 long-hauler patients is associated with platelet storage pool deficiency.

This prospective case-control study found that both classic POTS patients and post‑COVID (PASC) patients with POTS commonly report easy bruising and share a measurable platelet dense granule storage pool deficiency (δ‑SPD). Using electron microscopy to count dense granules per platelet (DG/PL), both POTS cohorts averaged about 2.5 DG/PL, significantly lower than controls (~4.2–4.3 DG/PL), with no significant difference between pre‑COVID and post‑COVID POTS groups. The findings suggest δ‑SPD is a frequent comorbidity in POTS, including long‑COVID POTS, and may help explain bleeding symptoms (e.g., easy bruising) and potentially other multisystem complaints. Clinically, awareness of δ‑SPD in POTS may prompt targeted hemostasis history-taking and consideration of platelet function evaluation in symptomatic patients.