Journal of Preventive Medicine & Infectious Diseases

Abstract

Background: In classical dengue, thrombocytopenia peaks during the critical phase and normalizes spontaneously in convalescence usually by10th 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 & 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.

Conclusions: 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.