Sialidosis type I: How to alleviate disabling myoclonic seizures?-A multicenter analysis of eight cases and review of the literature.

OBJECTIVE

Sialidosis type I (ST-1) is an autosomal-recessive, very rare, progressive lysosomal storage disorder caused by pathogenic variants in NEU1. It is clinically characterized by progressive ataxia, myoclonic seizures (MS), bilateral tonic-clonic seizures (BTCS), and distinctive ophthalmological findings. Given the lack of curative options, in this study, we investigated symptomatic treatment strategies, with a particular focus on the efficacy of antiseizure medications (ASMs).

METHODS

We describe the clinical course of a patient followed from diagnosis to 18 years of age, and review seven additional cases from our cohort. In parallel, we conducted a narrative review of the literature (PubMed, January 2010-September 2025) to identify published reports containing therapeutic data.

RESULTS

Therapeutic responses were evaluated in a total of 33 cases (8 from our cohort, 25 from published sources). Although available data are insufficient to define standardized treatment guidelines, some ASMs, such as ACZ, PER, LEV, VPA, CZP, and ZNS, demonstrated fairly consistent efficacy in managing MS and BTCS. Sodium oxybate or deep-brain stimulation may be considered in refractory cases.

SIGNIFICANCE: Prospective documentation of clinical course and treatment outcomes-ideally through an international registry-is crucial to improve patient care and inform therapeutic strategies.

PLAIN LANGUAGE SUMMARY: Sialidosis type I (ST-1) is a very rare genetic disorder causing movement problems and seizures, with no cure available yet. We followed 8 patients and reviewed 25 published cases to assess treatments focusing on myoclonic seizure (MS) control. Some antiseizure medications showed benefit. However, we have too little data to make clear recommendations. To improve patients' treatment and to choose the most appropriate therapy, it would be important to follow patients over a longer period of time, for example, in an international registry.