Background At disease onset, children with acute lymphoblastic leukaemia (ALL) may present with arthralgia or even signs of arthritis. This might cause misdiagnosis and thereby lead to prolonged diagnostic delay. The present study aimed to identify children with ALL with joint involvement and to compare their characteristics and outcome with children with ALL without joint involvement.

Methods Case records of 286 children diagnosed with ALL between 1992 and 2013 were reviewed and analysed in this retrospective, descriptive study.

Results Fifty-three (18.5%) children with ALL presented with localised joint pain, and half of them had objective signs of arthritis. The mean number of joints involved was 2.5, most frequently presenting as asymmetric oligoarthritis. The suspected misdiagnosis were reactive arthritis (19/53), osteomyelitis (9/53) and juvenile idiopathic arthritis (8/53). Children with joint involvement had less objective signs of haematological disease. Cytopenia was absent in 24% in children with joint involvement (vs 8% without, p=0.001), 50% had only one cell line affected (vs 21%, p=0.0005) and 44% had no organomegaly (vs 29%, p=0.05). Median diagnostic delay was 4 vs 2 weeks. The 5-year event-free and overall survival was superior for children with joint involvement: 94% vs 87% (p=0.049), and 96% vs 83% (p=0.044).

Conclusions ALL with joint involvement is a frequent finding (18.5%). The clinical signs of leukaemia are less prominent, but non-articular pain should alert the clinician of a possible diagnosis of leukaemia. The overall and event-free survivals were superior compared with the children without joint involvement.