Two cases of type I sialidosis and a literature review.

OBJECTIVE

This study aims to compare the clinical and electrophysiological characteristics of two cases of type I sialidosis in Chinese children with those reported in prior literature. The goal is to elucidate 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, who was admitted in June 2020, and a 10-year-old boy, admitted in July 2023, exhibiting rapid weight gain and accompanying visual impairment as primary manifestations. A literature review was performed by summarizing data from 31 published articles encompassing 69 genetically confirmed cases of type I sialidosis up to 2023 for comparative analysis.

RESULTS

Patient 1 exhibited short stature, self-reported poor night vision, a history of occasional febrile seizures, mild scoliosis, bilateral cherry-red spots in the fundus, and prolonged P100 latency in both eyes as observed in visual evoked potentials (VEP). Genetic analysis revealed that she carried compound-heterozygous variants c.239 C > T (p.P80L) and c.880 C > T (p.R294C) in the NEU1 gene, inherited from her parents. Patient 2 presented with rapid weight gain and visual impairment, bilateral cherry-red spots in the fundus, abnormal neuroepithelial layer reflexes 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.239 C > T (p.P80L) and c.803 A > G (p.T268C) were identified in the NEU1 gene of the Patient 2, inherited from his parents. By combining the cases reported in 31 literature articles with the 2 cases in our study, a total of 71 type I sialidosis patients were analyzed. The most common symptoms observed were muscle spasms (91.5%), followed by ataxia (75%) and seizures (63.6%). Intellectual impairment and abnormal electroencephalograms were more prevalent in Caucasian patients. Additionally, abnormal somatosensory evoked potentials, large cortical waves, and prolonged latency of VEP were more frequently observed in both Asian and Caucasian patients, serving as alternative indicators for early diagnosis.

CONCLUSION

NEU1 gene analysis provides essential guidance for genetic counseling and prenatal diagnosis. The exon 2 variant c.239 C > T (p.P80L) in the NEU1 gene may represent a mutation hotspot among Chinese patients.