Whole-exome sequencing revealed a mutation in the neuraminidase gene (NEU1) and established the diagnosis of sialidosis.<h4>Clinical discussion</h4>Sialidosis is a rare autosomal recessive type of lysosomal storage disease resulting due to mutation of the neuraminidase gene leading to intracellular accumulation of sialic acid compounds. The gene discussed is NEU1; the disease is sialidosis.