Heterogenic presentations of Sialidosis in two Sri Lankan children

Abstract

Background

Sialidosis is a rare autosomal recessive lysosomal storage disorder (LSD) caused by alpha-N-acetylneuraminidase enzyme deficiency due to mutations in neuraminidase NEU1 gene which results in accumulation of sialyloligosaccharides in lysosomes in various organs and tissues. Type 1 sialidosis is a mild and nondysmorphic form presents at second or third decade of life while type 2 is severe and dysmorphic, where affected individuals will present in utro, infantile and juvenile periods.

Case presentations

Herein we present two Sri Lankan children who were genetically diagnosed to have Sialidosis type 2. Case 1 presented at one month of age with abdominal distension since day 2 of life found to have coarse facies, failure to thrive, hepatoslenomegaly, ascites and anemia. Bilateral posterior embryotoxon was detected during ophthalmologic examination. It is a novel ocular feature in sialidosis which has not been mentioned before in the literature. Case two presented at the age of 8 years with unevaluated squint since age of 3 years and poor school performance. Bilateral cherry red spots were found following eye examination. Molecular characterization of case 1 showed novel allelic variant c.798+1G>A in NEU 1 gene which results from homozygous splicing pathogenic mutation. Compound heterozygous mutations were found in case 2 involving splicing pathogenic variant c.798+1G>A and a missence uncertain significant variant c.887 A>G.

Conclusion

Sialidosis type 2, a rare neuronal storage disorder may present with a variety of symptoms and signs. Sialidosis should be considered with uncommon presenting features such as abdominal distension and ascites. Though cherry red spots are common ocular manifestation, novel ocular features such as posterior embrayotoxon also should consider in storage disorders.