General description

Salla disease is a rare autosomal recessive lysosomal storage disorder caused by mutations in the SLC17A5 gene. It is characterized by the accumulation of sialic acid in lysosomes and is considered a mild form of Free Sialic Acid Storage Disease (FSASD). Unlike infantile sialic acid storage disorder (ISSD), which is caused by mutations in the same gene and is fatal in infancy, Salla disease has a slower progression and often allows survival into adulthood.

The disease primarily affects the central nervous system and presents early in life. Although infants appear normal at birth, symptoms such as hypotonia and nystagmus typically develop within the first year. Motor and cognitive impairments are common, including delayed motor milestones, speech difficulties (with expressive language more affected than comprehension), progressive ataxia, spasticity, and involuntary movements such as athetosis. Some patients exhibit mild coarse facial features, skeletal abnormalities, and hepatosplenomegaly. As the disease progresses, there is a gradual decline in motor function, sometimes leading to the loss of previously acquired skills like walking, alongside cognitive deterioration. However, the overall progression remains slow, and many individuals reach adulthood.

References

1. Sonninen, Pirkko, et al. "Brain involvement in Salla disease." American journal of neuroradiology 20.3 (1999): 433-443.