Infantile Central Nervous System Juvenile Xanthogranuloma With Somatic <i>CSF1R</i> Mutation Responsive to Imatinib Monotherapy

Juvenile xanthogranuloma (JXG) of the central nervous system (CNS) is a rare non-Langerhans cell histiocytosis. CSF1R mutations have been reported for peripheral JXG, but not in CNS JXG. A 3-month-old male presented with fever, lymphadenopathy, and macrocephaly with bulging fontanelles. Imaging demonstrated multiple dural-based masses causing obstructive hydrocephalus. The patient underwent right frontal endoscopic third ventriculostomy, choroid plexus cauterization, and craniotomy for resection and tissue diagnosis. Pathology was consistent with JXG, and NGS identified a somatic CSF1R mutation. Liquid imatinib monotherapy led to resolution of lesions and continued treatment response after 3 years without adverse events or drug interruptions.