MEN (General Swiss-German Mennonite)

Inheritance: autosomal recessive
Genes: SLC17A5

SD
Sialuria (Finnish type)

Developmental delay
Growth delay
Truncal ataxia
Spasticity
Limb dystonia
Diffuse hypomyelinization

Salla Disease

Clinical Characteristics

General description (for patients): 

Patients from infancy are slow to develop, both in physical growth and in motor function.  Early physical activites such as crawling and walking are often delayed and young children are noted to be unsteady and fall easily.  Often they are described as ‘clumsy’ with spasticity of the limbs.  Intellectual function and social interactions can be normal early.  Lifespan can also be normal although neurological deterioration does occur slowly and older individuals may become bedridden.

Medical description: 

This is the adult form of sialuria, a sialic acid storage disease.  This form is difficult to detect in infancy but motor milestones and linear growth delays are evident in young children, often with truncal ataxia and general clumsiness.  Deep tendon reflexes are brisk early but hypotonia is evident later.  Social interactions and early intellectual development are often normal.  Later, muscle wasting and dystonic movements of the limbs become evident.  Lifespan may be normal although ambulation can become a problem in the 5thand 6th decades.  Seizures are uncommon.  The MRI shows supratentorial hypomyelination with thinning of the corpus callosum.  Basal ganglia appear normal although swallowing difficulties have been reported.  Urine free sialic acid is elevated.

Genetics:

Salla disease is likely due to a defect in a lysosomal transmembrane transporter.  The mutation, located on chromosome 6 (6q14-q15), is in the SLC17A5 gene  A 115C>T substitution causes disease in the homozygous configuration (autosomal recessive).  It has been identified in numerous residents of northeastern Finland, but a kinship with 5 affected Mennonite individuals has been reported from eastern Pennsylvania.

Treatment:

 No treatment for this neurological disorder is available.

Prognosis:

A normal lifespan is possible although progressive neurological deterioration leads to severe restrictions.

Ancillary treatments and support: 

Most patients do well for many decades.

Specialists and specialty centers:

Neurologist, Physical Therapist, Pediatrician.

References: 

Strauss, K.A., Puffenberger, E.G., Craig, D.W., Panganiban, C.B., Lee, A.M., Hu-Lince, D., Stephan, D.A., and Morton, D.H.:  Genome-wide SNP arrays as a diagnostic tool: Clinical description, genetic mapping and molecular characterization of Salla disease in an Old Order Mennonite population.   Am. J. Med. Genet. 138A: 262-267, 2005.  PubMed: 16158439

Varho, T.T., Alajoki, L.E., Posti, K.M, Korhonen, T.T., Renlund, M.G., Nyman, S.R., Sillanpaa, M.L., and Aula, P.P.:  Phenotypic spectrum of Salla disease, a free sialic acid storage disorder.  Pediatr. Neurol. 26: 267-273, 2002.  PubMed:11992753

Verheijen, F.W., Verbeek, E., Aula, N., Beerens, C.E.M.T., Havelaar, A.C., Joosse, M., Peltonen, L., Aula, P., Galjaard, H., van der Spek, P.J.: A new gene, encoding an anion transporter, is mutated in sialic acid storage diseases.  Nature Genet. 23: 462-465, 1999.  PubMed: 10581036