trimethoprim intravenously every hours) should be considered if there are respiratory symptoms, with or without a positive chest radiograph Treatment for suspected PCP should not be delayed because of concern of interfering with the diagnostic workup Fungal infections, with the exception of oral thrush, are uncommon in HIV-infected children However, candidal sepsis should be considered in hospitalized patients who not improve with antibiotics Chronic fever is common in HIV-infected children and has a broad differential diagnosis The major focus of such an evaluation in the ED is to rule out acute bacterial infection A careful history and physical examination should be followed by a CBC, urinalysis, chest and sinus films, and blood, urine, and stool cultures Recurrent otitis media is commonly seen, and some children may have recurrent parotitis or sinusitis If no source is recognized on examination and the initial testing is negative, more unusual infections need to be considered Tuberculosis, although common among HIV-infected adults, is uncommon in children but may be more likely among adolescents Mycobacterium avium complex may cause chronic fevers in HIV-infected children This pathogen is often associated with anemia secondary to bone marrow infiltration and can be cultured from blood, stool, and bone marrow Numerous viruses can cause chronic infections associated with fever in these children EBV and CMV are among the more common, with CMV often presenting with chronic hepatitis and bloody diarrhea It may also cause pneumonia and retinitis A blood buffy coat specimen can be sent for quantitative CMV-antigen detection Most HIV-positive children with fever of unknown origin are hospitalized to facilitate the diagnostic process The possibility of drug fever must also be considered Two OIs warrant special attention: PCP and lymphoid interstitial pneumonitis (LIP) PCP is caused by a fungal pathogen and is the most common initial manifestation of HIV in the perinatally infected infant The infant or child typically is febrile, with marked tachypnea, wheezing, rhonchi, and diminished breath sounds Rales are not usually part of the PCP picture, and cough may be absent When coughing is present, it is typically dry and nonproductive Over hours to days, the patient develops hypoxia and increased respiratory distress Initial ED evaluation should include beginning supplemental oxygen, obtaining pulse oximetry, an arterial blood gas, a chest radiograph, and serum LDH levels Radiographs may show a diffuse interstitial (“ground-glass”) pattern, but infants may develop patchy infiltrates or complete opacification of the lung fields The diagnosis often requires bronchoscopy with specimens sent for silver stains However, if the ED physician suspects PCP, it is appropriate to start IV TMPSMZ at a dosage of mg/kg/dose of TMP every hours The child should be