Impulsivity, Compulsivity, Social Inappropriateness, and Other Neuropsychiatric Features in Cerebellar Histiocytosis.

Langerhans cell histiocytosis (LCH) may present with cerebellar and brainstem lesions associated with ataxia, cognitive impairment, and behavioral symptoms. While neuropsychiatric manifestations have been reported in LCH, little attention has been paid to impulsivity, compulsivity, and social inappropriateness in the context of cerebellar involvement. We describe six patients with multisystem LCH who developed neurological and psychiatric disturbances in association with cerebellar abnormalities on magnetic resonance imaging. Clinical, neuropsychological, and neuroimaging findings were reviewed, with a particular focus on impulsive-compulsive symptoms and social behavior. When serial imaging was available, the temporal relationship between symptom severity and cerebellar lesion evolution was reviewed. In addition, a systematic literature review was performed to identify previously reported neuropsychiatric manifestations associated with cerebellar LCH. Patients with more extensive cerebellar and brainstem involvement showed more prominent impulsive, compulsive, and socially inappropriate behaviors, whereas patients with restricted dentate abnormalities showed milder attentional and impulsive symptoms. Behavioral manifestations included hyperactivity, poor impulse control, hypersexuality, pathological gambling, substance abuse, aggression, and social inappropriateness. A notable finding was the temporal clinical-radiological association documented in one patient, the only case with neuroimaging obtained during and soon after psychiatric exacerbation. In this patient, psychiatric worsening paralleled progression of cerebellar lesions and later improved clinically and radiologically after immunomodulatory treatment. These cases expand the neuropsychiatric phenotype of cerebellar LCH by highlighting impulsivity, compulsivity, and social inappropriateness as underrecognized manifestations. Our findings support a possible contribution of cerebellar networks, particularly cerebello-limbic circuitry, to these behaviors and underscore the need for systematic behavioral assessment, longitudinal follow-up, and further studies on targeted therapeutic approaches.