A 1½-year-old female child presented with swelling in thoracolumbar region and delayed developmental milestones. The routine hemogram analysis on Sysmex XN 1000 showed flags of white blood cell (WBC) abnormal scattergram and lymphocytosis. The peripheral smear examination showed Alder-Reilly (AR) granules leading to a suspicion of underlying Mucopolysaccharidosis (MPS). Further clinical workup, radiographic studies, chemical test lead to the confirmatory diagnosis of MPS. A flag of abnormal WBC scattergram and AR anomaly are the hematological findings that can be seen in a case of MPS.