Purpose or Case Report: Pulmonary lesions have been found in fewer than 10% of children with a solitary site of involvement in Langerhans cell histiocytosis(LCH) but in 23%–50% of those with multisystem involvement. The established diagnostic procedures are lung biopsy and bronchoalveolar lavage with a score of more than 5% CD1a-positive cells. Scattered reports of LCH within the thymus exist, typically among children within the setting of multifocal, multisystem disease. Purpose of this presentation is overview of the diverse radiologic manifestations of lung and thymic involvement of Langerhans cell histiocytosis that may be observed with imaging, which allows exact depiction of the extent and severity of disease.
Methods & Materials: A retrospective analysis was conducted on children who presented with respiratory symptoms or abnormal lung radiologic findings, and finally diagnosed with LCH during the last 4 years. Thymic abnormalities as calcification and enlargment, and lung paranchymal disease as, cavitary lesions or intertitial patern, are noted on CT imaging.
Results: Histiocytic infiltration increases the size of the thymus, and the thymic enlargement may be noticeable even on initial chest radiographs. CT provides clearer depiction of the heterogeneously attenuating, diffusely enlarged thymus(figure1). Punctate or serpentine calcifications are typical features (figure2). The calcifications may be of vascular or dystrophic origin; their exact pathogenesis is not known. Cystic areas corresponding to focal lesions also may be observed within the enlarged thymus.
Initial chest radiographs show diffuse, bilateral, symmetric interstitial disease. Characteristic reticulonodular pattern that results from the summation of nodules and thin cystic walls (figure3) are seen on CT. The lung volume, unlike that in other interstitial diseases, mostly remains normal or may even be increased.
Conclusions: Thymic involvement in Langerhans cell histiocytosis has been reported infrequently. However, it probably has occurred more often than it has been recognized. All of the reported occurrences were associated with multisystem Langerhans cell histiocytosis. In many cases, there was coexistent pulmonary involvement. Lung involvement in Langerhans cell histiocytosis is not necessarily associated with an adverse outcome. However, the cystic lesions, emphysema, and fibrotic changes observed on radiologic images are persistent.