Introduction

Children with leukaemia may first present with musculoskeletal symptoms mimicking juvenile idiopathic arthritis and often have normal haematological variables.1 The correct diagnosis may be delayed because evaluation focuses on the arthritis. Treatment with steroids may be started early, which may delay diagnosis further and reduce the subsequent response to chemotherapy.2 We report a case, initially diagnosed as juvenile idiopathic arthritis, in which acute lymphoblastic leukaemia became apparent six months after presentation and only after treatment with both steroids and methotrexate. This case emphasises the importance of early bone marrow examination if there are any atypical features of juvenile idiopathic arthritis and certainly before starting steroids or cytotoxic agents.

Case report

A previously fit 7 year old boy with no relevant family history presented with a one month history of upper chest and shoulder pain. He had malaise, lethargy, and poor appetite but no history of night sweats. He was pale with low grade pyrexia of 37.8°C. Examination showed reduced range of movements in his shoulder joints, restricted by pain. All other joints were normal. Plain radiographs of the shoulder joints were normal. Erythrocyte sedimentation rate was raised at 90 mm/hour. Full blood count was haemoglobin 11.8 g/dl, platelets 249×10⁹/l, total white cell count 4.7×10⁹/l, and neutrophil count 2.0×10⁹/l. He was diagnosed as having musculoskeletal injury and was given ibuprofen.

Despite this he re-presented a month later after developing pain in his hip, knee, and ankle joints bilaterally associated with further malaise and lethargy. The pain was particularly prominent at night. He was systemically unwell but had no rash, lymphadenopathy, or hepatosplenomegaly. He had tenderness bilaterally over the anterior aspects of the tibia and his right knee was warm, tender, and swollen with an associated effusion. He was referred to the local paediatric team and …