1.Sialidosis Type I without a Cherry Red Spot— Is There a Genetic Basis?
Koti NEERAJA ; Vikram Venkappayya HOLLA ; Shweta PRASAD ; Bharath Kumar SURISETTI ; Kempaiah RAKESH ; Nitish KAMBLE ; Ravi YADAV ; Pramod Kumar PAL
Journal of Movement Disorders 2021;14(1):65-69
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.
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