Childhood-onset Erdheim-Chester disease in the molecular era: clinical phenotypes and long-term outcomes of 21 patients

TO THE EDITOR:

Erdheim-Chester disease (ECD) is a rare, systemic histiocytic disorder characterized by tissue infiltration by foamy CD68⁺ CD1a⁻ histiocytes.¹ Its clinical presentation ranges from a localized condition to a multisystem and life-threatening disease.² Patients with ECD have significantly benefited from the recent introduction of targeted therapies (ie, BRAF inhibitors [BRAFis], MEK inhibitors [MEKis], and mammalian target of rapamycin inhibitors),^3-5 but some still have a refractory course or experience long-term disability.⁶ 

ECD typically occurs in adulthood, and data on pediatric cases have so far been sporadic. Therefore, the most appropriate diagnostic and therapeutic approach in children remains uncertain. An additional challenge in diagnosing pediatric ECD resides in the pathologic similarity with juvenile xanthogranuloma (JXG), which displays similar morphology and immunostaining features.^2,7 However, JXG is usually a localized cutaneous disease, and its...