Differential Diagnosis of Thrombotic Microangiopathy: Overlapping Features of Thrombotic Thrombocytopenic Purpura and Complement-Mediated Thrombotic Microangiopathy in a Dengue-Infected Patient.

Background: Thrombotic microangiopathy (TMA) encompasses a group of rare, life-threatening disorders characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ damage, most commonly affecting the kidneys. Complement-mediated TMA (CM-TMA), a subtype of TMA, is often associated with dysregulation of the complement system due to genetic mutations. Dengue virus has been recognized as a potential trigger of secondary TMA and may precipitate CM-TMA in genetically predisposed individuals.

Case presentation: We report the case of a 47-year-old woman with a history of thrombotic thrombocytopenic purpura (TTP) who presented with fever, gastrointestinal symptoms, anemia, thrombocytopenia, and acute kidney injury. Dengue infection was confirmed by a positive NS1 antigen. Laboratory and peripheral smear findings indicated TMA. Therapeutic plasma exchange was started due to previous history of TTP, with partial clinical response. ADAMTS13 activity was preserved at 60.7%. Kidney biopsy demonstrated features of TMA. Genetic testing identified a heterozygous pathogenic variant in the CD46 gene, supporting the diagnosis of CM-TMA. Notably, the patient showed sustained clinical improvement without the use of eculizumab.

Conclusion: This case illustrates the diagnostic challenges of TMA in patients with overlapping clinical features and potential infectious triggers. In dengue-endemic regions, the virus should be recognized as a possible precipitating factor for TMA, particularly in individuals harboring complement gene mutations. A multidisciplinary approach - integrating clinical, laboratory, histopathological, and genetic data - is essential for accurate diagnosis and personalized management of TMA syndromes.