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October 2001 (continued)
 In an HIV-infected child, common respiratory processes include Pneumocystis carinii pneumonia (PCP), bacterial and viral pneumonitis, and lymphoid interstitial pneumonitis (LIP)/pulmonary lymphoid hyperplasia (PLH). Of these, LIP/PLH is associated with a chronic course and digital clubbing.
 LIP/PLH belongs to a spectrum of lymphoid processes of the respiratory system. LIP/PLH is thought to be associated with Epstein-Barr virus infection. It is usually diagnosed after the first year of life in children with vertical HIV infection. This is in contrast to PCP, which is most commonly diagnosed in the first year of life. Patients with LIP/PLH may be clinically asymptomatic. Evidence of lung disease appears with the development of tachypnea, cough, wheezing, and hypoxemia. The disease may present with extra-pulmonary lymphoid proliferation including lymphadenopathy, hepatosplenomegaly, and parotid gland enlargement. Recurrent superimposed respiratory infections occur. As the disease becomes more advanced, digital clubbing may develop. While rales often are present, they are not considered a sign of LIP/PLH. Instead, rales indicate the presence of concurrent superimposed infections. Pulmonary function tests generally show a restrictive pattern with some patients having obstructive symptoms such as wheezing. The natural course of LIP/PLH is indolent and chronic, sometimes culminating with chronic bronchiectasis and cystic lesions.
Definitive diagnosis of LIP/PLH requires microscopic examination of lung tissue (obtained via open lung biopsy), although a presumptive diagnosis often is made on clinical grounds alone. LIP/PLH is considered when the clinical history and physical findings described above occur in an HIV-infected child and other illnesses (e.g., tuberculosis) have been excluded. A chest radiograph suggestive of LIP/PLH will have a reticulonodular pattern that persists for greater than 2 months despite adequate anti-microbial therapy.
Once the diagnosis of LIP/PLH has been established, treatment can be initiated. Current treatment includes starting or adjusting antiretroviral therapy with the goal of reducing the viral load and increasing the CD4+ cell count. Adjuvant therapy includes pulmonary toilet, antibiotics, and physical therapy for acute exacerbations and superimposed infections. Patients with wheezing may benefit from therapy with bronchodilators. Hypoxic patients should improve with oxygen supplementation. If there is evidence of advanced disease, including digital clubbing and hypoxemia with an oxygen saturation less than 90, systemic corticosteroids may be started. Management of LIP/PLH should also include measures to prevent secondary infections. As such, these children should receive the polyvalent pneumococcal and Haemophilus influenzae type b conjugate vaccines. They also should be vaccinated annually against influenza A and B viruses.
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