Research has established that childhood leukemia with MSK involvement mimics various conditions, which often results in diagnostic delays. Moreover, the clinical implication of MSK involvement in childhood leukemia on survival outcomes is inconclusive. In a recent publication in the journal, Pediatric Rheumatology, researchers attempted to compare characteristics and survival outcomes between MSK and non-MSK involvement in childhood leukemia.

The researchers retrospectively reviewed the medical records of pediatric patients under age 15 years who received an acute leukemia diagnosis between January 1978 and December 2019. The information recorded for each child included demographic characteristics, clinical manifestations at diagnosis, and initial laboratory investigations such as CBC, blood chemistry, subtype of acute leukemia (acute lymphoblastic leukemia [ALL] or acute myeloid leukemia [AML]), and year of diagnosis.

The researchers also reviewed the MSK symptoms of each patient, with involvement identified as bone and/or joint pain in terms of arthralgia or arthritis. The researchers defined arthralgia as "pain localized in one or more joints" and arthritis as "joint pain with signs of joint inflammation (joint swelling, effusion, redness, increased heat, or limited range of motion)." Joint involvement patterns were identified as monoarticular (one joint), oligoarticular (2 to 4 joints), and polyarticular (5 or more joints). Moreover, initial radiographs were reviewed for radiographic bone changes in leukemia including metaphyseal radiolucent bands, osteolytic lesions, osteosclerosis, and periosteal reaction.

During the 42-year period, the researchers discovered that of the 1,042 childhood leukemia cases, 81 (7.8%) children had MSK involvement at initial presentation. They also found that MSK involv ment was more likely in children with ALL than AML (P <.05). Hematologic abnormalities occurred less frequently in the MSK involvement group (P <.05), and the absence of peripheral blast cells was significantly greater in the MSK involvement group (17.3% vs. 9.6%, P = .04). Normal CBCs with absence of peripheral blast cells were observed in 2.5% of the children with MSK involvement. With regard to propensity score-matching for comparable risk groups of children with and without MSK involvement, the 5-year overall survival was not significantly different (48.2% vs. 57.4%, respectively, P = .22), nor was event-free survival (43.3% vs. 51.8%, respectively, P = .31).

Other differences between the cohorts included a "slightly higher" initial onset of disease among patients with MSK involvement. Additionally, patients with MSK involvement were more likely to be diagnosed with ALL (88.9%) than AML (11.1%).

The authors concluded, "Childhood leukemia with MSK involvement had the notable characteristics of minimal or absent hematologic abnormalities and peripheral blast counts. The survival outcomes were not different between those with and without MSK involvement. As the clinical and laboratory signs of leukemia can be obscured at initial presentation, clinicians should be aware of the possibility of leukemia in children who present with MSK complaints."

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