Familial haemophagocytic lymphohistiocytosis. A report of three cases with unusual lung involvement.

Three cases of familial haemophagocytic lymphohistiocytosis are presented with lung infiltration by haemophagocytic histiocytes. In all patients the diagnosis was based on hepatosplenomegaly, thrombocytopenia and anaemia, abnormal increase in triglycerides, ferritin and LDH, hypofibrinogenaemia and lymphohistiocytosis with haemophagocytosis in bone marrow. Two patients died of respiratory failure due to interstitial pneumonia. In these two patients the pneumonia was obscured and misinterpreted by the pathologists. A careful re-examination revealed lymphohistiocytosis and haemophagocytic cells within the lung parenchyma. The third patient showed alveolar wall infiltration by haemophagocytic histiocytes and lymphocytes. In early childhood acute or recurrent interstitial pneumonia should prompt a search for haemophagocytic histiocytes, and familial haemophagocytic lymphohistiocytosis should be included in the differential diagnosis.