J Mov Disord.  2021 Jan;14(1):65-69. 10.14802/jmd.20083.

Sialidosis Type I without a Cherry Red Spot— Is There a Genetic Basis?

Affiliations
  • 1Department of Neurology, National Institute of Mental Health and Neurosciences, Karnataka, India
  • 2Department of Clinical Neurosciences, National Institute of Mental Health and Neurosciences, Karnataka, India

Abstract

Sialidosis is an inborn error of metabolism due to a defect in the NEU1 gene and manifests as two phenotypes: mild type I and severe type II. The cherry red spot (CRS) is a characteristic feature in both types of sialidosis; reports of sialidosis without a CRS are rare. We report two cases of genetically confirmed sialidosis type I with a typical presentation of progressive cortical myoclonus and ataxia but without the CRS. A previously reported homozygous pathogenic variant p.Arg294Cys was detected in the first case, and a novel homozygous pathogenic variant p.Arg305Pro was detected in the second case. Additionally, we reviewed the literature describing cases with similar mutations to find a genetic basis for the absence of a CRS. Milder mutation of both alleles detected in both patients may be the reason for the absence of a CRS.

Keyword

Ataxia; Cherry red spot; Mild mutation; Myoclonus; Sialidosis type I
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