A family of Niemann-Pick disease type C caused by compound heterozygous mutations in NPC1 gene / 中华神经科杂志

ABSTRACT

Objective:To report the clinical and genetic characteristics of a family with Niemann-Pick disease type C caused by novel compound heterozygous mutations in the NPC1 gene to improve the clinicians′ recognition of the disease. Methods:Two patients from the family with non-consanguineous marriages admitted to the Department of Neurology of the First Affiliated Hospital of Kunming Medical University in 2020 were examined in detail. Peripheral blood DNA was extracted, and whole exome sequencing was performed on the patients, combined with Sanger sequencing for verification. The mutation and protein function predictor softwares were applied to analyze the mutation sites.Results:The inheritance was autosomal recessive in this family. The onset age of the proband was 9 years, and the main clinical manifestations were dysarthria, dysphagia, cognitive impairment, ataxia, bilateral pyramidal tract impairment, vertical supranuclear gaze palsy and splenomegaly. The clinical phenotype of the proband′s younger brother was similar to that of the proband, but it was more severe than that of the proband. The younger brother of the proband had an earlier age of onset and severe psychomotor retardation. Whole exome sequencing showed that both brothers carried 2 rare variants of NPC1 gene:1 pathogenic, stop gain at c.352_353del, p.Gln119ValfsTer8, and a missense change, c.593A>G, p.Asn198Ser, of suspected pathogenic. Sanger sequencing confirmed that compound heterozygous mutations were derived from the proband′s parents. According to the American College of Medical Genetics and Genomics guidelines, the above variants were rated as pathogenic and suspected pathogenic, respectively. And the c.593A>G, p.Asn198Ser mutation found in this family was a novel one which had not been reported yet. The proband had delayed diagnosis for 7 years from the onset of symptoms. After taking megastat for 1 year, the symptoms of dysphagia, ataxia and vertical eye movement disorder were significantly improved. Conclusions:The clinical phenotype of the pedigree was consistent with the clinical phenotype of Niemann-Pick disease type C. Compound heterozygous mutations of NPC1 gene (c.352_353del; c.593A>G) were found to be the genetic cause of the family.