Chronic Diffuse Interstitial Lung Disease in Childhood



Chronic Diffuse Interstitial Lung Disease in Childhood


Iley Browning

Claire Langston



Chronic diffuse interstitial lung disease in children includes a heterogeneous group of pathologic states characterized by a diffuse inflammatory process that involves the interstitium or supporting structures of the lung as opposed to the alveolar spaces. Interstitial pneumonia is a nonspecific reaction to injury that can be a manifestation of infection, drugs, toxic inhalants, collagen vascular disease, or a variety of genetic, metabolic, or inflammatory disorders.


ETIOLOGY

Diffuse interstitial lung disease in children can be classified in numerous ways. Classification by etiology and by age at presentation is particularly useful (Box 240.1). Age at presentation is an important factor when considering the diagnostic possibilities because a group of conditions exist that are seen only in newborns and infants but not in older children. Newborns and near-term infants who present with early respiratory failure and fail to respond to conventional therapies should be assessed for developmental and genetic disorders, including deficiency of surfactant proteins B and C and abnormality of ABCA3, a transporter protein thought to be involved in surfactant secretion, the structural abnormality known as alveolar capillary dysplasia with misalignment of pulmonary veins, congenital alveolar dysplasia, and other abnormalities of intrauterine lung growth. The disease processes that present exclusively in infants include persistent tachypnea of infancy (also known as neuroendocrine hyperplasia of infancy), infantile cellular interstitial pneumonitis (also known as pulmonary interstitial glycogenosis), and chronic pneumonitis of infancy (now widely thought to be the histologic appearance of some surfactant dysfunction mutations, more often surfactant C protein deficiency). Most cases of pulmonary alveolar proteinosis seen in children, as well as the histologic appearance of some of surfactant dysfunction mutations, also present in infants.



CLINICAL MANIFESTATIONS AND COMPLICATIONS

These diseases are all uncommon occurrences, and many are poorly understood. The usual clinical presentation is insidious
onset and minimal early findings, although acute fulminate presentation can occur. Tachypnea is the hallmark physical finding and may be the only early finding, although occasionally acute presentation with tachypnea, hypoxemia, and fever may occur. Older children may present with dyspnea, with or without wheezing, whereas infants and toddlers more frequently present with tachypnea without respiratory distress. Fine crackles often are present with progression of disease. Symptoms overlap with those of common respiratory infections, but the prolonged course, lack of response to initial therapies, and imaging findings will separate these processes from the more common acute pulmonary infections. The chest radiograph may be normal initially, but later it often shows a diffuse interstitial pattern of reticulonodular infiltrate. Chest computed tomography (CT) scan generally is a more sensitive indicator of disease activity and shows better correlation with symptoms than does chest radiograph. Separating the various disease processes that produce chronic diffuse interstitial lung disease may be difficult using clinical, laboratory, and radiologic findings, and frequently lung biopsy is necessary to define the pathologic process.


LUNG DISEASE PRESENTING IN NEWBORNS


Genetic Deficiency of Surfactant Protein B

Lung disease on the basis of a genetic abnormality of surfactant protein B is a rare, chronic, diffuse lung disease seen in young infants. Affected infants generally present soon after birth with hypoxia and respiratory distress; chest radiographs shows a ground-glass appearance; investigations for infectious etiologies are negative. The diagnosis can be made by performing appropriate studies on blood (for the genetic abnormality) and lavage fluid (for the surfactant protein B deficiency) and lung biopsy. Surfactant replacement is not a viable therapy. Some affected infants have been treated with lung transplantation with good results. The picture on lung biopsy varies, with some infants having the classic picture of pulmonary alveolar proteinosis, whereas others have less prominent proteinosis and instead have a picture of alveolar epithelial hyperplasia with relatively limited amounts of proteinosis material, and still others have conditions that resemble chronic pneumonitis of infancy.

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Jul 24, 2016 | Posted by in ORTHOPEDIC | Comments Off on Chronic Diffuse Interstitial Lung Disease in Childhood
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