A case of neurodegenerative Langerhans cell histiocytosis exhibiting high osteopontin in cerebrospinal fluid without specific radiological abnormalities

Neurodegenerative Langerhans cell histiocytosis (ND-LCH) manifests several years after onset of LCH, with progressive neurological symptoms and characteristic brain imaging features. Although ND-LCH has a dismal neurological prognosis, distinct treatment strategies are not available owing to the unknown pathophysiology. We describe the case of a 6-year-old boy who developed left convergent strabismus four years after onset of multisystem LCH (MS-LCH). Although radiological imaging showed no abnormalities, the osteopontin level in the cerebrospinal fluid (CSF-OPN) was highly elevated without other abnormal CSF findings, leading to a diagnosis of ND-LCH. The patient received monthly intravenous immunoglobulin therapy for four years, without symptoms worsening. To investigate the relevance of OPN levels in LCH, we retrospectively analyzed serum and CSF OPN levels in eight LCH patients. Serum OPN levels were markedly elevated in the two MS-LCH patients with macrophage activation (400 and 445 ng/mL) compared to the other six patients (mean: 59 ng/mL). CSF-OPN levels were elevated in the ND-LCH patient (620 ng/mL) compared to the two patients with pituitary involvement (160 and 182 ng/mL), suggesting that the pathophysiology of ND-LCH reflects its inflammatory status. Analysis of CSF-OPN levels would be a useful tool to detect and treat ND-LCH.