Background: Adenovirus infections are common in children, usually presenting as mild upper respiratory illness. However, in high-risk patients such as those with Down syndrome and congenital heart disease, adenovirus can cause severe pneumonia and acute respiratory distress syndrome (ARDS). No specific antiviral treatment is routinely available, but cidofovir has been used off-label in refractory cases.Case Presentation: We report a 1.5-year-old male with Down syndrome, congenital heart disease (patent ductus arteriosus, secundum atrial septal defect, small pericardial effusion), and hypothyroidism on levothyroxine. The patient presented with fever, cough, and progressive respiratory distress. Initial management included high-flow nasal cannula, followed by intubation due to worsening hypoxemia. Laboratory evaluation showed severe anemia, elevated CRP, neutrophilia, lymphopenia, and thrombocytosis, with preserved renal function.Chest CT revealed bilateral pleural effusions, total consolidation of the left lung, and scattered right-sided consolidations. Thoracic ultrasound confirmed effusions (10 mm on the right, up to 2 cm on the left) and a consolidated right lung. Blood, tracheal aspirate, and pleural fluid cultures were sterile, while adenovirus PCR was positive.Despite empirical piperacillin-tazobactam and amikacin, there was no clinical improvement. The patient underwent surgical decortication due to a complicated pleural effusion. Postoperatively, cidofovir was initiated. The patient showed marked clinical recovery, was successfully extubated, and discharged in good condition.Learning Points:- Adenovirus pneumonia can progress to life-threatening disease in children with Down syndrome and comorbidities.- Negative bacterial cultures with adenovirus PCR positivity supported a viral etiology.- Cidofovir may be considered a therapeutic option in refractory adenovirus pneumonia, provided renal function is preserved.- Surgical decortication, followed by cidofovir, contributed to recovery in this complex case.- Multidisciplinary management, including pediatric intensive care, infectious disease, and surgery, is essential for optimal outcomes.
