Pulmonary Langerhans cell histiocytosis
Shortness of breath. Current smoker.
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Multiple bilateral cysts with scattered nodules. Lung volumes are preserved on the scout image. Predominance in the upper and mid-zones, with sparing of the costophrenic angles (particularly on the left).
Prominent lymph nodes are seen. Further scattered ground glass shadowing.
The combination of lung nodules and cysts is virtually diagnostic for Langerhans cell histiocytosis. Unlike lymphangioleiomatosis, lung nodules are present, the cysts have irregular outlines, and the lung bases are spared. Lymphadenopathy is an atypical feature of LCH. Ground glass opacity may be seen and can reflect associated DIP or RB-ILD.
25% will develop a pneumothorax at some stage. Other complications are pulmonary hypertension (from LCH involvement of the pulmonary vasculature). Regression of the radiographic findings can be seen in up to a third of patients.
Definitive diagnosis requires surgical lung biopsy, but this is now performed only when the imaging appearances are not typical. Occasionally, the diagnosis can be made by transbronchial biopsy or lavage.