Hurler syndrome

Alternative names

Alpha-L-iduronate deficiency; Mucopolysaccharidosis type I; MPS I

Definition

Hurler syndrome is an inherited disease that belongs to a group of diseases called mucopolysaccharidoses. Storage of abnormal quantities of this material (mucopolysaccharide) in different body tissues is responsible for the symptoms and appearance of the disease.

Causes, incidence, and risk factors

Hurler syndrome is inherited as an autosomal recessive trait. The metabolic defect that causes Hurler syndrome is the body's inability to make an enzyme called lysosomal alpha-L-iduronate.

Approximately 1 in 150,000 infants are affected. Newborn infants with this defect appear normal at birth but, by the end of the first year, signs of impending problems begin to develop. The children slowly develop coarse, thick, facial features, prominent dark eyebrows, cloudy corneas, progressive stiffness, and obvious mental retardation.

The disease damages many organs including the heart and heart valves. In the early onset form of the disease, death occurs in the early teens, often from the associated heart disease.

Symptoms

• Short stature
  
• Severe mental retardation
  
• Thick, coarse facial features with low nasal bridge
  
• Full lips with a thick, large tongue
  
• Cloudy corneas
  
• Increased body hair (hirsutism)
  
• Umbilical hernia
  
• Deafness
  
• Stiffness (in joints)
  
• Shortness of breath
  
• Abnormal bones of spine and claw hand
  

Signs and tests

• Hepatomegaly
  
• Splenomegaly
  
• Inguinal hernia
  
• Flared nostrils
  
• Epicanthal folds
  
• Enlarged tongue
  
• Retinal pigmentation
  
• Hip dislocation
  
• Vertebral wedging
  
• Kyphosis
  
• Heart murmurs
  
• Heart valve damage from thickening
  

Tests that may indicate the syndrome is present include: