Sialidosis (also called mucolipidosis type I) and galactosialidosis are rare disorders of glycoprotein metabolism. Sialidosis is subdivided into type I, the milder form, where there is an ocular cherry red spot and generalised myoclonus in the second decade, and type II where there is an early-onset progressive MPS-like phenotype with visceromegaly and mental retardation. Galactosialidosis is subdivided into early infantile, late infantile and juvenile/adult types. There is a spectrum of many of the features typically seen in storage disorders, and resemblance to both GM1-gangliosidosis and sialidosis.
a-N-acetylneuraminidase and b-galactosidase are assayed to diagnose sialidosis and galactosialidosis.
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