An aggressive systemic juvenile xanthogranuloma clonally related to a preceding T-cell acute lymphoblastic leukemia.

Juvenile xanthogranuloma (JXG) is a disorder of disputed origin thought to be related to the dermal/interstitial macrophage. A 5-year-old female presented with an aggressive systemic JXG that developed 5 months after the diagnosis of T-cell acute lymphoblastic leukemia (T-ALL). Examination of the T-cell receptor gamma (TCR-γ) rearrangement in T-ALL blasts, JXG infiltrated lymph node biopsies and micro-dissected JXG histiocytes revealed an identical bi-allelic TCR-γ rearrangement in all samples, thus providing evidence for a clonal relationship between T-ALL and JXG in this case.