Autosomal recessive
MPS-plus syndrome is caused by changes in both copies of VPS33A, which helps deliver material to lysosomes for recycling. Glycosaminoglycans build up as in the mucopolysaccharidoses, but the standard lysosomal enzymes work normally. Most reported people carry the same variant, p.Arg498Trp, and many are from the Yakut population of Siberia.
Signs and symptoms
The severe form starts in infancy, with features similar to the mucopolysaccharidoses, and urine tests can show raised glycosaminoglycans. Unlike typical mucopolysaccharidoses, kidney disease, heart defects and blood (haematopoietic) disorders are reported. The condition is often life-limiting in early childhood.
What a diagnosis changes
There is no specific treatment; care is supportive, with kidney, heart, blood and developmental monitoring and treatment of complications. Genetic counselling is recommended; parents are usually carriers, and carrier testing can be offered to relatives.
Genes analysed
Also known as
MPSPS; mucopolysaccharidosis-like plus disease; mucopolysaccharidosis-like syndrome with congenital heart defects and hematopoietic disorders
