We describe the case of an infant with immune thrombocytopenia whose bone marrow showed an increased percentage of CD10/TdT-positive lymphoid cells that resembled the onset of an acute lymphoproliferative disorder. Genotypic analysis of bone marrow, however, failed to reveal the malignant origin of these B cell precursors. After 8 months of follow-up, the child is alive and well, and shows a chronic form of ITP. Although a relation between this B cell proliferation and the onset of ITP cannot be excluded, it is important to consider this atypical pattern as a benign hematologic condition.