Acute lymphoblastic leukaemia presenting as chronic recurrent multifocal osteomyelitis.

A pre-schooler, born out of a non-consanguineous marriage, presented with on-and-off fever for 9 months, fleeting large joint swelling involving multiple joints for 5 months, weakness and pain in different limbs for 5 months, and difficulty in breathing for 2 weeks, 3 months ago. Initial differentials considered were haematogenous osteomyelitis and systemic-onset juvenile idiopathic arthritis. There was no rash, lymphadenopathy or hepatosplenomegaly. The initial bone marrow biopsy showed chronic inflammation and normal haematopoietic cells. The child developed septic arthritis in the right knee during hospitalisation. After excluding malignancy, chronic recurrent multifocal osteomyelitis was diagnosed, and anti-inflammatory medication was prescribed. Subsequently, the child exhibited pancytopenia and hepatosplenomegaly 2 months after hospital stay, and further bone marrow biopsy confirmed acute lymphoblastic leukaemia. This case underscores the importance of maintaining a vigilant approach to leukaemia when children present with musculoskeletal symptoms, as early detection and treatment are crucial for improving outcomes in childhood acute leukaemia.