Histiocytosis x, pulmonary

(also called Langerhans cell histiocytosis or eosinophilic granuloma of the lung), an uncommon idiopathic disease characterized in its early stages by granulomatous nodules containing Langerhans histiocytes and eosinophils, which are primarily peribronchial. In its later stages, the cellular granulomas are replaced by fibrosis and the formation of cysts; pneumothorax occurs in up to 20%. The majority of patients with pulmonary histiocytosis X are young or middle-aged adults presenting with nonspecific symptoms of cough and dyspnoea. Over 90% of patients are smokers, and a causal relationship with smoking is likely.

The radiographic findings consist of reticular, nodular and cystic patterns, often in combination. Abnormalities are usually bilateral, involving predominantly the middle and upper lung zones, with relative sparing of the costophrenic angles. Lung volumes are characteristically normal or increased.

HRCT findings include thin-walled lung cysts, usually less than 10 mm in diameter. Although many cysts appear round, they can also have bizarre shapes, being bilobed, cloverleaf-shaped, or branching in appearance. In the majority of cases, small nodules are also present (Fig.1); larger nodules may be cavitary. In nearly all cases, the lung bases and the costophrenic sulci are relatively spared.

RW