ESPE Abstracts

Objective: This study aims to compare the clinical and electrophysiological characteristics of two cases of type I sialidosis in Chinese children with previously reported cases, in order to elaborate the clinical and genetic features of type I sialidosis.

Methods: Clinical investigations and genetic analyses were conducted on an 11-year-old girl primarily presenting with short stature, admitted in June 2020, and a 10 years boy, admitted in July 2023, with rapid weight gain and accompanying visual impairment as the main manifestations. A literature review was performed by summarizing data from 31 published articles on 69 genetically confirmed cases of type I sialidosis up to 2023 for comparison.

Results: Patient 1 presented with short stature, self-reported poor night vision, a history of occasional febrile seizures, mild scoliosis, bilateral cherry-red spots of fundus, and prolonged P100 latency in both eyes on visual evoked potentials (VEP). She carried compound-heterozygous variants c.239C>T (p.P80L) and c.880C>T (p.R294C) in the NEU1 gene, inherited from her parents. Patient 2 presented with rapid weight gain and visual impairment, fundus cherry-red spots, abnormal neuroepithelial layer reflex in both macular areas, approximately normal P100 latency but severely reduced amplitude in VEP after pupillary dilation, and severe bilateral optic nerve conduction block with relatively normal retinal cell function. Compound-heterozygous variants c.239C>T (p.P80L) and c.803A>G (p.T268C) has been identified in his NEU1 gene, inherited from his parents. Combining the cases reported in 31 literature articles and 2 cases in our study, a total of 71 type I sialidosis patients were analyzed. The most common symptoms were muscle spasms (91.5%), followed by ataxia (75%) and seizures (63.6%). Intellectual impairment and abnormal electroencephalograms were more common in Caucasian patients. Abnormal somatosensory evoked potentials, large cortical waves, and prolonged latency of VEP were more frequent in Asian and Caucasian patients, serving as alternative indicators for early diagnosis.

Conclusion: Mucopolysaccharidosis is a rare genetic disorder. The analysis of two cases of type I sialidosis in mainland China emphasizes the importance of NEU1 gene analysis in diagnosing type I sialidosis, thereby providing essential guidance for genetic counseling and prenatal diagnosis. The exon 2 variant c.239C>T (p.P80L) in the NEU1 gene may be a mutation hotspot for Chinese patients.