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an autosomal recessive disorder due to a deficiency of sialidase; there are two different types: Type I is of adolescent or adult onset and is characterized by myoclonus, ocular cherry red spot with progressive loss of visual acuity, and storage of sialyloligosaccharides. Type II is additionally characterized by somatic abnormalities, coarse facial features, and dysostosis multiplex and occurs as several variants of increasing severity with earlier age of onset; the one in neonates is accompanied by ascites, facial edema, inguinal edema, and early death; the one in infants is accompanied by visceromegaly and mental retardation; and a juvenile form is better characterized as galactosialidosis.
cher·ry-red spot my·oc·lo·nus syn·drome
a neuronal storage disorder in children characterized by a cherry-red spot at the macula, progressive myoclonus, and easily controlled seizures; the result of sialidase deficiency. Type I is characterized by normal body habitus, cherry-red macula, myoclonus, and normal β-galactosidase levels; type II by short stature, bony abnormalities, and deficient β-galactosidase.
Either of two types of mucolipidosis caused by a deficiency of the enzyme neuraminidase (formerly called sialidase) and characterized by myoclonic seizures, cherry-red maculas in the retina with visual impairment, enlarged liver and spleen, and intellectual disability in the more severe type.
a neuronal storage disease of children caused by a deficiency of the enzyme sialidase (neuraminidase). The condition is characterized by a cherry-red spot on the macula, progressive myoclonus, and seizures. There are two types. Type 1 patients have normal physical features and beta-galactosidase levels. Type 2 patients also have short stature, bony abnormalities, and beta-galactosidase deficiency.
sialidosisA condition caused by an isolated defect of alpha-N-acetyl neuraminidase (sialidase) in leukocytes and fibroblasts and an increase of sialyloligosaccharide in the urine. Sialidosis is divided into two types:
• Type 1, or cherry-red spot myoclonus syndrome, which is characterised by myoclonic epilepsy, visual problems and ataxia in the 2nd or 3rd decade of life; macular cherry-red spots are 100% present. The myoclonus is aggravated by smoking and menses, among other factors, and may become debilitating.
• Type 2 patients have an earlier onset of symptoms and exhibit dysmorphic and somatic features that progressively worsen. Type 2 is subdivided into:
– Infantile-onset form—Presents in the first year of life with coarse, Hurler-like facies; hepatomegaly; bony changes of dysostosis multiplex; developmental delay; and cherry-red spots (occur in < 75%); and
– Congenital form—Onset in utero, with hydrops fetalis and hepatomegaly; infants are either stillborn or die within months.