Neuroleptic malignant syndrome in Huntington disease

Despite the wide use of dopamine receptor blocking agents (DRBAs) in Huntington disease (HD), neuroleptic malignant syndrome (NMS) is rarely described in this population. The aim of this study was to assess NMS prevalence in a large cohort of HD patients and explore the main associated risk factors.

In 2023, an HD patient was admitted to our neurology department due to NMS. Starting from the case description, we performed a narrative review of the literature of NMS cases in HD, reviewed data from the fifth dataset of the Enroll-HD (a longitudinal, observational, global study of families with HD) study (PDS5) selecting HD patients treated with DRBAs and/or tetrabenazine (TBZ) who presented at least one of the core symptoms of NMS (rigidity and hyperthermia), and collected data to investigate prevalence of NMS and identify risk factors.

In the Enroll-HD PDS5 dataset, we identified 5108 of 11,569 HD patients who were undergoing DRBA and/or TBZ treatment. Only one patient, a Caucasian man of 46 years, undergoing clozapine and valproate treatment, had a registered diagnosis of NMS.

NMS in HD patients is seldom described. This could be due to an underestimation of this condition. There are no available objective NMS diagnostic criteria at present, and the existence of atypical forms of NMS further complicates diagnosis. Advanced disease stage, rigid-akinetic phenotype, abrupt therapy changes, polytherapy, and dehydration are key risk factors, most of which are preventable through awareness and caution in managing medications in the HD population.