Hurler syndrome, also known as mucopolysaccharidosis Type IH (MPS-IH), Hurlers disease, and formerly gargoylism, is a genetic disorder that results in the buildup of large sugar molecules called glycosaminoglycans (GAGs) in lysosomes. The inability to break down these molecules results in a wide variety of symptoms caused by damage to several different organ systems, including but not limited to the nervous system, skeletal system, eyes, and heart. The underlying mechanism is a deficiency of alpha-L iduronidase, an enzyme responsible for breaking down GAGs. : 544  Without this enzyme, a buildup of dermatan sulfate and heparan sulfate occurs in the body. Symptoms appear during childhood, and early death usually occurs. Other, less severe forms of MPS Type I include Hurler-Scheie Syndrome (MPS-IHS) and Scheie Syndrome (MPS-IS). Hurler syndrome is classified as a lysosomal storage disease. It is clinically related to Hunter syndrome (MPS II); however, Hunter syndrome is X-linked, while Hurler syndrome is autosomal recessive. Signs and symptoms
Children with Hurler syndrome may appear normal at birth and develop symptoms over the first years of life. Symptoms vary between patients.One of the first abnormalities that may be detected is coarsening of the facial features; these symptoms can begin at 3–6 months of age. The head can be large with prominent frontal bones. The skull can be elongated. The nose can have a flattened nasal bridge with continuous nasal discharge. The eye sockets may be widely spaced, and the eyes may protrude from the skull. The lips can be large, and affected children may hold their jaws open constantly.
A person born with one normal copy and one defective copy is called a carrier. They will produce less α-L-iduronidase than an individual with two normal copies of the gene. The reduced production of the enzyme in carriers, however, remains sufficient for normal function; the person should not show any symptoms of the disease. Mechanisms
The IDUA gene is responsible for encoding an enzyme called alpha-L-iduronidase. Through hydrolysis, alpha-L-iduronidase is responsible for breaking down a molecule called unsulfated alpha-L-iduronic acid. This is a uronic acid found in the GAGs dermatan sulfate and heparan sulfate. The alpha-L-iduronidase enzyme is located in lysosomes. Without sufficient enzymatic function, these GAGs cannot be digested properly. Diagnosis
Diagnosis often can be made through clinical examination and urine tests (excess mucopolysaccharides are excreted in the urine). Enzyme assays (testing a variety of cells or body fluids in culture for enzyme deficiency) are also used to provide definitive diagnosis of one of the mucopolysaccharidoses. Prenatal diagnosis using amniocentesis and chorionic villus sampling can verify if a fetus either carries a copy of the defective gene or is affected with the disorder. Genetic counseling can help parents who have a family history of the mucopolysaccharidoses determine if they are carrying the mutated gene that causes the disorders. Classification
All members of the mucopolysaccharidosis family are also lysosomal storage diseases. Mucopolysaccharidosis type I (MPS I) is divided into three subtypes based on severity of symptoms. All three types result the absence or decreased functioning of the same enzyme.