Non-Langerhans histiocytosis mimicking sarcoidosis on high-resolution computed tomography

The non-Langerhans histiocytoses (NLH) are a group of very rare disorders characterized by a predominantly cutaneous proliferation of non-Langerhans histiocytes. Involvement of the respiratory system is rare and more frequently affects the airways than the lung parenchyma. We describe a 44-year-old man with the progressive nodular form of NLH, with known cutaneous and hepatic involvement. High-resolution computed tomography performed for the investigation of his breathlessness revealed an interstitial pattern of disease closely resembling sarcoidosis. Lung biopsy showed non-Langerhans histiocytic infiltration of the lung parenchyma. Radiologists should be aware of NLH as a mimic of pulmonary sarcoidosis.