From Myositis to Electrolyte Crisis: A Case Report of Dengue-Associated Rhabdomyolysis and Salt-Wasting Syndrome

<p><strong>Background: </strong>Dengue fever is a common arboviral infection that is typically self-limiting, but rare complications such as myositis, rhabdomyolysis, and electrolyte disturbances can pose diagnostic and therapeutic challenges.</p> <p><br /><strong>Case Presentation:</strong> We report a patient with dengue confirmed by non-structural 1 antigen who initially improved with supportive care but re-presented with severe myalgia, tea-colored urine, and markedly elevated creatine kinase (54,000 U/l), consistent with rhabdomyolysis. Her symptoms were refractory to hydration and analgesia but responded rapidly to corticosteroids. Subsequently, she developed polyuria and profound hypotonic hyponatremia with inappropriately concentrated urine and high urinary sodium, consistent with renal salt wasting syndrome (RSW). Management required careful fluid resuscitation to maintain euvolemia and intermittent desmopressin to control polyuria. Autoimmune screening revealed positive anti-ribonucleoprotein antibodies and anti-Ro antibodies, suggesting an immune-mediated process. She achieved full recovery with normalization of muscle enzymes and electrolytes.</p> <p><br /><strong>Conclusion:</strong> This case highlights the diverse and clinically significant complications of dengue, including immune-mediated myositis and RSW. Importantly, distinguishing RSW from SIADH is crucial, as their treatments differ substantially and misclassification may worsen outcomes.</p>