Mucolipidosis III gamma
Mucolipidosis III gamma is a slowly progressive, rare genetic disorder characterized by skeletal abnormalities, joint stiffness, and a shortened lifespan.
Overview
Mucolipidosis III gamma is a slowly progressive disorder that affects many parts of the body. Signs and symptoms typically appear around age 3. Individuals with this condition generally survive into adulthood, though they may have a shortened lifespan.
Symptoms
- Slow growth and short stature
- Stiff joints and pain that worsens over time
- Dysostosis multiplex (multiple skeletal abnormalities seen on x-ray)
- Low bone mineral density, leading to weakened bones and fractures
- Osteoporosis
- Heart valve abnormalities
- Mild clouding of the clear covering of the eye (cornea)
- Slightly thickened or coarse facial features
- Mild intellectual disability or learning problems in a small percentage of cases
Causes
This condition is caused by mutations in the GNPTG gene. This gene provides instructions for making a subunit of the enzyme GlcNAc-1-phosphotransferase. This enzyme is responsible for "tagging" digestive enzymes with a molecule called mannose-6-phosphate (M6P), which acts as a signal to transport these enzymes to the lysosomes—the cell's recycling compartments.
Mutations in the GNPTG gene reduce the activity of this enzyme, preventing digestive enzymes from reaching the lysosomes. Consequently, large molecules accumulate within the lysosomes, characterizing this as a lysosomal storage disorder.
Inheritance
This condition is inherited in an autosomal recessive pattern, meaning both copies of the gene in each cell have mutations. Parents of an affected individual typically carry one copy of the mutated gene but do not show signs or symptoms of the condition.
Other Names
- ML IIIC
- Mucolipidosis III
- Mucolipidosis III, variant
- Mucolipidosis IIIC
- Mucolipidosis type III
- Pseudo-Hurler polydystrophy