Sialidosis Type I without a Cherry Red Spot— Is There a Genetic Basis?
Koti Neeraja, Vikram V. Holla, Shweta Prasad, Bharath Kumar Surisetti, Kempaiah Rakesh, Nitish Kamble, Ravi Yadav, Pramod Kumar Pal
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.