Introduction: The osteoarticular manifestations revealing acute leukemia in children are diverse and can be source of diagnostic delay, especially in the absence of other signs that point to a malignant origin.

Case Report: We report through this case of a 4-year-old boy without any medical history and who consulted in our department for isolated severe pain in the left hip bone causing sleep deprivation, occurred after a minimal trauma and causing lameness, all symptoms dated back to 15 days before admission. Clinical examination was normal. Radiological assessment was normal as well. Mild anemia with neutropenia was noted on the blood count with no inflammatory signs. The blood smear was normal. The bone marrow aspiration confirmed the diagnosis of acute B-cell lymphoblastic leukemia.

Discussion: Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy. Osteoarticular manifestations of ALL in children are rare, they are revealing ALL in 14% of cases.The musculoskeletal symptoms can be so prominent or even the only presenting sign that sometimes the diagnosis of leukemia is delayed.

Conclusion: Knowledge of orthopedic manifestation of leukemia is important in the diagnosis, supportive treatment and follow up of patients in order to improve their survival.