Cytomegalovirus Infection in an Extremely Preterm Infant: A Diagnostic Challenge.

Cytomegalovirus (CMV) infection in the extremely preterm infant represents a major diagnostic challenge: its clinical manifestations overlap with comorbidities inherent to prematurity, underlying immunodeficiency may suppress viral replication below detectable thresholds, and the diagnostic window for confirming congenital infection closes irreversibly at 21 days of life. An extremely preterm female infant (26 weeks, 800 g) had a neonatal course complicated by bronchopulmonary dysplasia, leukoencephalopathy, and chorioretinitis - findings that, individually, were attributable to prematurity. CMV was not tested within the 21-day diagnostic window. A plasma CMV PCR at day 44, triggered by clinical deterioration, returned negative. At 70 days of life, severe multilobar pneumonia with respiratory failure requiring high-frequency oscillatory ventilation developed without an identifiable bacterial aetiology. Targeted bronchoalveolar lavage confirmed CMV at 136,000 IU/mL, markedly dissociated from simultaneous plasma viraemia of 9,910 IU/mL. Primary combined immunodeficiency (T⁻/B⁺/NK⁺ pattern) was diagnosed simultaneously. Ganciclovir therapy achieved progressive viral load reduction. In the extremely preterm infant, CMV may remain clinically invisible behind more immediate diagnoses. A negative plasma CMV PCR does not exclude active infection in the setting of combined immunodeficiency. Severe multisystem deterioration without an identified aetiology should prompt site-directed CMV investigation and simultaneous immunological evaluation.