1 | INTRODUCTION
Juvenile xanthogranuloma (JXG), the most common form of non-Langerhans cell histiocytosis (LCH), is thought to arise from dermal dendrocytes or macrophages. The majority of patients with the disease present primarily with skin lesions, which usually regress spontaneously. However, some patients develop extracutaneous lesions, with or without cutaneous lesions (i.e., systemic JXG); sometimes, these lesions can progress rapidly and can reduce quality of life, or even become life-threatening, despite aggressive LCH-oriented chemotherapy.1,2Similar to other histiocytic disorders such as LCH and Erdheim–Chester disease (ECD), patients with systemic JXG often harbor somatic mutations in the mitogen-activated protein kinase (MAPK) pathway genes, most notably BRAF.3
LCH affects the central nervous system, manifesting primarily as diabetes insipidus, or more rarely as neurodegenerative disease (ND). LCH-associated ND, characterized by progressive radiological abnormalities of the cerebellum, basal ganglia, and pons, as well as cerebellar dysfunction accompanied by cognitive impairment and behavioral disturbance, can develop many years after treatment for LCH.4 Involvement of multiple organ systems, particularly the pituitary gland, skin, base skull, or orbit bone involvement, and presence of the BRAF V600E mutation, are risk factors for developing LCH-associated ND.5
ND also occurs in patients with ECD;4 however, there is no report about ND in patients with JXG. Here, we report two cases of JXG who presented with radiological abnormalities similar to those observed for LCH-associated ND.