Hypereosinophilia: A rare presentation of acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) presenting as peripheral blood hypereosinophilia is very rare and the incidence is <1%. The characteristic feature of patients with ALL and hypereosinophilia is the absence of blasts in peripheral blood, and this might lead to misdiagnosis of ALL. It is important for clinicians and pathologists to be aware of this uncommon initial presentation of ALL to avoid delay in diagnosis. We report a 37-year-old man who presented with fever and respiratory symptoms and was found to have hypereosinophilia in peripheral blood. His bone marrow and lymph node biopsies were diagnostic of ALL.