A rare lysosomal storage disease, and the severe, early onset form of sialidosis characterized by a progressively severe mucopolysaccharidosis-like phenotype (coarse facies, dysostosis multiplex, hepatosplenomegaly), macular cherry-red spots as well as psychomotor and developmental delay. ST-2 displays a broad spectrum of clinical severity with antenatal/congenital, infantile and juvenile presentations. The disease is Monarch Disease Ontology identifier MONDO_0009738 (sialidosis type 2). Also known as: NEU1 sialidosis, dysmorphic sialidosis, dysmorphic sialidosis with renal involvement, infantile dysmorphic sialidosis, mucolipidosis I, mucolipidosis type I, nephrosialidosis, sialidosis caused by mutation in NEU1.