Hypereosinophilia syndrome with pneumonia in acute lymphoblastic leukaemia.

Eosinophilic pneumonia in association with acute lymphoblastic leukaemia (ALL) is very rare. A teenage boy is described with eosinophilic pneumonia which preceded by several months the onset of ALL. Prior to establishment of the diagnosis he had been treated with corticosteroids with a transient response only. This delayed his final diagnosis until there were haematologic features of leukaemia. The leukaemic blasts were cALLA (CD10) positive and had a normal chromosome number with no translocations on banding studies. The pneumonia remitted rapidly when his leukaemia responded to chemotherapy.