Relapsing nodular lesions in the course of adult pulmonary Langerhans cell histiocytosis.

In most patients with pulmonary Langerhans cell histiocytosis (LCH), clinical and radiological abnormalities initially either stabilize or regress, often without treatment. Little information is available, however, concerning the subsequent evolution of disease in patients who initially follow a benign course. We describe four patients with biopsy-confirmed pulmonary LCH whose initial course was characterized by regression of parenchymal nodular lesions, but who subsequently developed one or more episodes of active disease 7 mo to 7.5 yr after their initial presentation. In each case, the subsequent episodes of active disease were characterized by the reappearance or marked increase in nodular radiographic abnormalities, whose presence was confirmed by high-resolution computed tomography (HRCT). Thus, initial regression of nodular lesions in pulmonary LCH does not preclude the reappearance of one or more episodes of active disease, and may have important consequences on the long-term prognosis of these patients.