Mucopolysaccharidosis 1 (MPS I) is a rare lysosomal storage disease from the group of mucopolysaccharidoses. Due to an autosomal recessive inherited enzyme defect of the lysosomal enzyme alpha-L-iduronidase, glycosaminoglycans can no longer be sufficiently split and degraded.
Instead, they are stored in the lysosomes of the body's cells. In particular, dermatan sulfate and heparan sulfate are deposited.
There are three variants, which vary considerably in severity: The most severe form is Hurler syndrome, the mildest is Scheie syndrome. An intermediate phenotype is the Hurler-Scheie syndrome. The main symptoms of the severe and most frequent form (MPS I-H) are skeletal deformities and delayed motor and intellectual development.
The symptoms start in the first year of life. Other symptoms include corneal clouding, dwarfism, valvular cardiomyopathy, hernias, facial dysmorphism, gibboccal kyphoscoliosis, and hirsutism. In contrast, in patients with the mild form (MPS I-S) that occurs in adulthood, the central nervous system is not clinically affected, mental development is normal, and most patients have no mental retardation.
Patients reach a normal height, but usually suffer from joint stiffness and corneal opacities. Patients with the intermediate form (MPS I-H / S) have normal or near-normal intelligence, but are physically impaired to varying degrees. Phenotypically characteristic of the Hurler syndrome is the so-called "gargoylism". This manifests itself in doughy thickened skin, coarsened facial features, bulging lips, macroglossia, shaggy hair, macrocephalus and growth retardation.
Life expectancy is normal or only slightly reduced in Scheie syndrome. In contrast, patients with Hurler's syndrome die of severe cardiovascular and respiratory complications between the ages of eight and ten.