A 3-year-old boy of Romanian origin was admitted with the inability to weight bear and pyrexia. He was investigated to rule out septic arthritis. He subsequently developed an atypical clinical picture of fleeting joint arthritis, spiking temperature with poor response to antibiotics and atypical results of investigations. The peripheral blood smear showed a normal leukocyte count, but evidence of blast cells. Bone marrow aspirate confirmed the diagnosis of acute lymphoblastic leukemia. His skeletal radiographic survey had shown evidence of symmetrical metaphyseal sclerosis in the long bones, which has not been previously described as an isolated feature of acute lymphoblastic leukemia. Following a good response to chemotherapy, partial resolution of the sclerosis occurred. This case illustrates that metaphyseal sclerosis can be one of the manifestations of acute lymphoblastic leukemia and delay in diagnosis can easily occur in the absence of classic features of the disease. An early diagnosis is a good prognostic feature of these childhood malignancies.