[Pulmonary histiocytosis X].

This is a report on 2 adult patients suffering from pulmonary histiocytosis X. The aetiology and the diagnostic and therapeutic approach are discussed on the basis of a review of the literature. This is a rare disease that is triggered by a virus and immunologically conditioned, the disposition being genetically transferred. It is characterised by cells known as histiocytosis X cells with typical X bodies and immunocytochemically identifiable S 100 antigen. It will usually be necessary to perform an open biopsy of the lung to determine the histology of histiocytosis X. Roentgenologically pathognomonic signs are in particular ring-shaped structures of up to 5 mm diameter with a marginal edge. Lung function analysis revealing hypoxaemia after stress and, less significantly, diffusion capacity and vital capacity, are also among the most sensitive data pointing to histiocytosis X. Indication for treating the patients, who usually do not display prominent signs and symptoms, should be discrete because spontaneous remissions occur very frequently. If the patients display relevant signs and symptoms, corticosteroid long-term treatment over 12 months with 0.5-1.0 mg/kg body weight per day is recommended employing a slowly and progressively reduced dosage schedule. Chemotherapeutic drugs or thymus extracts are administered in a few rare instances.