Hurler-Scheie syndrome, also known as MPS I (Mucopolysaccharidosis Type I, Hurler syndrome, or Hurler Scheie syndrome), is a rare genetic disorder caused by the body’s inability to produce an enzyme that breaks down complex sugars. This leads to a buildup of harmful substances in various tissues and organs that can affect physical and cognitive development. It is a lysosomal storage disorder (LSD), which is a group of diseases that all arise from the body’s inability to break down and recycle different waste products. The symptoms of MPS I include skeletal abnormalities and impaired growth, heart and respiratory problems, various eye complications, hearing impairment and in some cases, cognitive impairment. The heart is affected in all individuals leading to issues such as valve problems, thickening of the heart muscle or obstructed blood flow, requiring careful monitoring.
Hurler syndrome is inherited in an autosomal recessive manner. This means a child must inherit two nonworking copies of the gene for alpha-L-iduronidase (IDUA)—one from each parent—to develop the disorder. Parents who each carry one copy of the affected gene are known as carriers and do not show symptoms; however, with each pregnancy they have a 25% chance of having an affected child.
In some regions, newborn screening includes a test for MPS I. This test measures enzyme levels to detect the condition at birth, allowing for timely intervention that can improve long-term outcomes. The state newborn screening lab in Austin is currently validating tests to add the condition to the newborn screen in Texas next year.
Treatment typically involves enzyme replacement therapy (ERT) to slow the progression of symptoms, and in severe cases, hematopoietic stem cell transplantation (HSCT) is used. Early intervention is crucial to improving outcomes and quality of life. Patients with MPS I also require multidisciplinary care, involving specialists from various fields to manage the heart, bones, respiratory system and other affected areas. This complex care is best coordinated through experienced centers as ongoing follow-up is essential to monitor and address new symptoms as they arise.
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