sialidosis; mucolipidosis 1; lipomucopolysaccharidosis; sialidase deficiency; glycoprotein neuraminidase deficiency; neuraminidase 1 deficiency; cherry red spot-myoclonus syndrome
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Classification
- sialidosis type 1 (milder form, normosomatic type)
- sialidosis type 2 (dysmorphic type)
Epidemiology
rare
Pathology
- deficiency of the enzyme neuraminidase
- progressive lysosomal storage of sialidated glycopeptides & oligosaccharides
- accumulation &/or excretion of sialic acid covalently linked to a variety of oligosaccharides &/or glycoproteins
- cytoplasmic vacuolation of peripheral lymphocytes, bone marrow cells & conjunctival epithelial cells
Genetics
- defects in NEU1 are the cause of sialidosis
- chromosomal rearrangement involving CTL4 & NEU1
Clinical manifestations
- presentation (infancy to 3rd decade of life)
- type 1:
- late-onset
- formation of macular cherry red spots in childhood
- progressive debilitating myoclonus
- insiduous visual loss
- ataxia (rare)
- type 2:
- occurs as several variants of increasing severity with earlier age of onset
- abnormal somatic features
- coarse facies
- dysostosis multiplex
- short trunk
- barrel chest
- vertebral deformities
- macular cherry red spots
- inner ear hearing loss
- neurologic abnormalities
- muscular hypotonia & hypotrophy, ataxia, myoclonus, & seizures, cerebellar syndrome, intellect low-normal, progressive neurodegeneration
- early demise, depending upon severity
Laboratory
- sialic acid in urine
- urine sialyloligosaccharide (present)
- sialuria