RESUMEN
Influenza virus primarily affects the respiratory system. It rarely causes extrapulmonary complications, with otitis media and febrile seizures being the most common in children. Acute glomerulonephritis as a complication of H1N1 influenza virus infection has been described only sporadically. Herein we present a case of acute glomerulonephritis in a previously healthy adolescent, in the context of infection with influenza A H1N1 virus. A 15-year old adolescent was admitted to our pediatric department due to fever, pharyngitis, cough, vomit, dizziness and fatigue. Based on his symptoms and the seasonal epidemiology, empiric treatment with oseltamivir was initiated while waiting for RT-PCR for influenza virus in pharyngeal swab, which was positive for A H1N1 influenza virus. In the first 24â¯h of admission, the patient presented macroscopic haematuria, which completely subsided in the following days, along with fever recession. The urine microscopic analysis showed findings compatible with acute glomerulonephritis. The patient remained normotasic while his biochemical profile including renal function, as well as further investigation of hematuria (immunoglobulins, C3, C4, ANA, anti-DNA, U/S) were all normal. ASTO levels, which were initially above normal (562â¯IU/ml), did not increase significantly in the following days, and given the fact that C3 levels were constantly within normal limits and pharyngeal culture was negative for pyogenic streptococcus, they were not considered sufficient for poststreptococcal glomerulonephritis diagnosis. Physicians should be suspicious and include influenza in the differential diagnosis when children present with uncommon symptoms such as hematuria along with even mild respiratory symptoms, during seasonal influenza period.