Talat MA, Allah MAN, Khalifa NA, et al. - In this prospective case-control study, researchers sought to assess the mean platelet volume (MPV) as a marker for disease activity in children with systemic lupus erythematosus (SLE). The sample consisted of 50 patients with SLE and 50 age and sex, matched healthy controls. The SLE group's MPV value was substantially higher than that of the control group. Significant increases in weight, blood pressure, urea, creatinine, proteinuria, CRP, ESR, cholestrol, MPV values, SLEDAI-2K scores and significant decreases in HB, albumin, C3, mean platelet volume (MPC) were observed in the active stage rather than in the remission stage. In active stage of the disease, there was a significant negative association between MPV and MPC but in remission stage, the association was negligible. MPV increased in active phase of patients with SLE and can be an easy, rapid, inexpensive and simple method to assess disease activity in children with SLE. In the active phase of SLE patients, MPV has increased and can be an easy, rapid, inexpensive and simple method of assessing disease activity in SLE children.