EC Microbiology

Background: In classical dengue, thrombocytopenia peaks during the critical phase and normalizes spontaneously in convalescence usually by 10^th day of illness. A minority of patients, however, remain profoundly thrombocytopenic after convalescent phase. Whether dengue can precipitate secondary immune thrombocytopenia (ITP) is under-recognized.

Methods: We conducted a single-center, prospective case-control study (July 2024 - May 2025) at Ad-din Women’s Medical College and Hospital, Dhaka. Among NS1 and/or RT-PCR-confirmed adults, cases had platelet counts < 50,000 µL^-1 persisting ≥ 10 days after illness onset, while controls showed no spontaneous recovery by day 14. We excluded common secondary causes of ITP (HBV, HCV, HIV, SLE, drugs, pregnancy). Cases received high-dose dexamethasone 40 mg daily for 4 days; controls received standard supportive care only. The primary end-points were platelet counts on days 11 and 15.

Results: Fifty patients (34 cases, 16 controls) were enrolled. Baseline characteristics were comparable. On day 11, mean platelet counts were similarly low (cases 40 471 ± 4775 vs controls 37 063 ± 6598 µL^-1; P = 0.043). By day 15, cases had risen to 319 353 ± 93 717 µL^-1 while controls remained at 48 438 ± 7908 µL^-1 (P < 0.001). All 34 cases achieved a clinically meaningful platelet response; no serious adverse events attributable to steroids were observed.

Conclusion: Persistent isolated thrombocytopenia after defervescence in convalescent phase dengue is uncommon but clinically important. In carefully phenotyped patients, a short course of high-dose corticosteroids-after exclusion of other secondary causes-produced rapid, sustained platelet recovery. These data support the concept of dengue-associated secondary ITP and justify larger multicenter trials.

Keywords: Dengue; Immune Thrombocytopenic Purpura; Persistent Thrombocytopenia; Convalescent Phase; Dexamethasone

1. Low JG., et al. “The early clinical features of dengue in adults”. PLOS Neglected Tropical Diseases12 (2011): e1191.
2. Verma SP., et al. “Corticosteroid-responsive thrombocytopenia in dengue fever: a case report”. BMJ Case Reports (2013): bcr2013200249.
3. Tam DTH., et al. “Effects of short-course oral prednisolone in early dengue infection: a randomized, placebo-controlled trial”. Clinical Infectious Diseases 9 (2012): 1216-1224.
4. Bandara SR and Herath HM. “Effectiveness of corticosteroid in the treatment of dengue - a systematic review”. Heliyon9 (2018): e00816.
5. Azeredo EL., et al. “Thrombocytopenia in dengue: interrelationship between virus and the imbalance between coagulation and fibrinolysis and inflammatory mediators”. Mediators of Inflammation (2015): 313842.
6. Chen HR., et al. “Dengue virus nonstructural protein 1 induces vascular leakage through macrophage migration inhibitory factor and autophagy”. PLOS Neglected Tropical Diseases7 (2016): e0004828.
7. Riswari SF., et al. “Desialylation of platelets induced by von Willebrand factor is a novel mechanism of platelet clearance in dengue”. PLoS Pathogens3 (2019): e1007500.
8. Lee TH., et al. “Potential harm of prophylactic platelet transfusion in adult dengue patients”. PLOS Neglected Tropical Diseases3 (2016): e0004576.
9. Estcourt LJ., et al. “Prophylactic platelet transfusion for prevention of bleeding in patients with haematological disorders after chemotherapy and stem cell transplantation”. Cochrane Database of Systematic Reviews 5 (2012): CD004269.
10. Goh ZJ., et al. “Transfusion of blood products and clinical outcomes for patients with dengue fever: a systematic review and meta-analysis”. Open Forum Infectious Diseases 9 (2024): ofae507.
11. World Health Organization. “Dengue: Guidelines for diagnosis, treatment, prevention and control”. 3^rd Geneva: WHO (2009).
12. Neunert C., et al. “American Society of Hematology 2019 guidelines for immune thrombocytopenia”. Blood Advances 23 (2019): 3829-3866.
13. Mazzucconi MG., et al. “Therapy with high-dose dexamethasone (HD-DXM) in previously untreated patients affected by idiopathic thrombocytopenic purpura: a GIMEMA experience”. Blood4 (2007): 1401-1407.
14. Wills BA., et al. “Coagulation abnormalities in dengue hemorrhagic fever: serial investigations in 167 Vietnamese children with dengue shock syndrome”. Clinical Infectious Diseases 3 (2002): 277-285.
15. Vaughn DW., et al. “Dengue viremia titer, antibody response pattern, and virus serotype correlate with disease severity”. Journal of Infectious Diseases 1 (2000): 2-9.