Lysosomal Storage Disorders: Mucopolysaccharidoses

Overview

• Mucopolysaccharidoses are types of lysosomal storage disorders.
• Unlike sphingolipidoses, no biochemical pathway memorization is required.
• Focus on understanding manifestations, distinguishing disorders, and involved enzymes.
• Two disorders to know: Hurler Syndrome and Hunter Syndrome.

Mucopolysaccharides

• Also known as glycosaminoglycans.
• Highly polar polysaccharides in connective tissue (bone, cartilage, heart valves).
• Accumulation causes defects in these tissues.

Common Features of Hurler and Hunter Syndrome

• Facial manifestations in children referred to as "gargoylism" (similar to acromegaly).
  • Frontal bossing
  • Prominent facial bones
  • Flattened nasal bridge
  • Hypertelorism
  • Macroglossia (enlarged tongue)
• Accumulation of mucopolysaccharides due to inability to degrade them.
  • Chiefly heparin sulfate and dermatan sulfate.

Hurler Syndrome

• More severe facial features and corneal clouding.
• Can involve hepatosplenomegaly and airway obstruction.
• Enzyme Deficiency: Alpha L-iduronidase
  • Remember: "L" in both "Hurler" and "L-iduronidase".
• Inheritance: Autosomal recessive.

Hunter Syndrome

• Milder version of Hurler Syndrome with potential aggressive behavior.
• No corneal clouding.
  • Mnemonic: "Hunters need to see their target."
• Inheritance: X-linked (occurs in males).
• Mnemonic for behavior: "Hunters shoot", indicating aggression.

Important Points

• Both disorders show accumulation of heparin sulfate and dermatan sulfate.
• Key characteristic features are facial manifestations resembling acromegaly.
• Hurler Syndrome: Severe features, corneal clouding.
• Hunter Syndrome: Mild features, no corneal clouding, aggressive behavior.

Review these key points to understand and distinguish Hurler and Hunter Syndromes, their features, enzymes involved, and inheritance patterns. Remember the mnemonics as aids to recall the differences and similarities between the two disorders.