Free sialic acid storage disease
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Summary
Free Sialic Acid Storage Disease (SSD) or Salla disease is a lysosomal storage disease. It is a very rare disease(except in Northern Finland where an estimated 1 in 40 people are carriers). Its clinical manifestations are heterogenous. Severe forms (Infantile Sialic Acid Storage Disease, ISSD) present in utero (with fetal hydrops and ascites) or at birth (with hypotonia, hepatosplenomegaly often associated with ascites, coarse facies, bone malformations, severe motor disorders, intellectual deficit, and seizures). Severe forms are fatal in early childhood. Individuals with the moderate form (initially described in Finland as Salla disease) present with hypotonia during the first year of life. The disease may progress to include spasticity, ataxia, psychomotor retardation, and sometimes coarse facial features. Most patients survive until adulthood but have profound intellectual deficit. The disease is caused by a defective sialic acid transporter (called sialin) in the lysosome membrane. This transporter normally ensures the efflux of free sialic acid (or N-acetylneuraminic acid) from the lysosome. The disease is transmitted in an autosomal recessive recessive manner. The causative gene is located on chromosome 6 and several mutations have been reported. Biologically, increased urinary excretion and storage of free sialic acid in fibroblasts, the trophoblast, or amniocytes, are diagnostic. Treatment is symptomatic only. *Authors: Dr R. Froissart, Dr I. Maire (February 2005)*.
Clinical signs
- Anaemia
- Chronic inflammatory lung disease
- Decreased skin pigmentation diffuse
- Long philtrum
- Mental retardation(degree not assessed)
- Splenomegaly
- Storage liver disease
- Auditory processing defect
- Hydrocephaly
- Hypertelorism
- Nephrotic syndrome
- Proteinuria
- Talipes-varus/valgus
- Umbilical hernia
Update : 15/04/2007
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