Mucolipidosis Type II (ML II or I-Cell Disease)
What is mucolipidosis type II (I-cell Disease)?
Inclusion-cell (I-cell) disease is the very severe second type of mucolipidosis, which is a group of metabolic disorders that affect the body’s ability to perform normal processes that involve the turnover of materials within cells. It is a metabolic disorder that is progressive, meaning it gets more severe as time goes on. While the exact frequency of I-cell disease is unknown, it is estimated to appear in about 1 in 100,000 to 400,000 people. It affects males and females equally.
People with I-cell disease may be mistakenly diagnosed with Hurler syndrome, as the symptoms are similar but tend to be more severe.
What are the symptoms of mucolipidosis type II (I-cell Disease)?
Some symptoms may be present at birth, and others develop fairly quickly during infancy. It is important to note that each individual may not have every symptom listed here. They include:
- At birth, small stature, weak muscle tone, and weak cry
- Coarse facial features
- Multiple abnormalities of the skull and face, such as: long and narrow head, unusually high and narrow forehead, skin folds on the inner corners of the eyes, and/or depressed nasal bridge
- Stunted growth and development in the first months of life
- Abnormal skeletal development, like scoliosis, swelling at the top part of the spine, dislocated hips, and/or short hands and fingers
- Severe delay in the development of speech and fine motor skills (like sitting and standing)
- Restricted joint movement
- Unusually thick and tight skin on certain body parts
- Development of a clouding on the cornea of the eyes
- Mental retardation
- Recurring ear infections that can lead to hearing loss
- Low muscle tone
- Short stature (dwarfism)
- Overgrowth of the gums
- Fingers that are fused together
- Recurring respiratory tract infections (pneumonia, middle ear infections, and bronchitis)
- Enlarged liver, spleen, and/or heart valves
- Constipation and/or diarrhea
- Congestive heart failure
What causes mucolipidosis type II (I-cell Disease)?
I-cell disease happens because of a mutation that causes a deficiency in an enzyme called N-acetylglucosamine-1-phosphotransferase. This enzyme tags other enzymes, telling them where to go. When it doesn’t tag the other enzymes, they escape the cell and thus don’t go where they’re supposed to. This results in the accumulation of other substances within the cells, which leads to the symptoms of the disorder.
To learn more about how the mucolipidoses are caused and inherited, click here.
How is mucolipidosis type II (I-cell Disease) diagnosed?
A major way to diagnose I-cell disease is examining tissues under a microscope for inclusion bodies. Inclusion bodies are masses of waste products (including proteins, carbohydrates, and proteins) that accumulate during this disease. The presence of inclusion bodies usually provides a diagnosis.
I-cell disease is also diagnosed using the following procedures:
- Before birth through amniocentesis and/or chorionic villus sampling (CVS)
- Thorough clinical evaluation
- Recording of patient history
- Specialized lab testing
What are the treatments for mucolipidosis type II (I-cell Disease)?
I-cell disease treatment is supportive and catered to the symptoms of each individual patient. It includes:
- Antibiotics to treat respiratory infections
- Yearly flu shots
- Physical therapy
- Total hip replacement
- Hearing aids
- Sleep studies
- In the case of heart problems, surgery
- Genetic counseling
Where can I find out more about mucolipidosis type II (I-cell Disease)?