Mucolipidosis Type IV (ML IV)

What is mucolipidosis type IV?

Mucolipidosis type IV is the fourth 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 characterized by significantly delayed motor and intellectual development, as well as worsening vision impairment. The severe form of this disease is called typical mucolipidosis IV, and the milder form is called atypical mucolipidosis IV. About 95% of people with this condition have the more severe form. Symptoms usually appear within 3 to 8 months after birth. Mucolipidosis type IV occurs in approximately 1 in 40,000 people. Research indicates that about 70% of people with this disease have Ashkenazi Jewish ancestry. It affects males and females equally. Occasionally, patients with this disease are misdiagnosed with cerebral palsy.

What are the symptoms of mucolipidosis type IV?

Patients with typical mucolipidodis type IV may show these symptoms:

Significantly delayed movement development and coordination
Moderate to severe intellectual disability
Severely impaired vision that gets worse over time
Severely impaired speech
Clouding on the cornea of the eye
Unsteady gait
Inability to walk independently
Difficulty chewing and swallowing
Weak muscle tone that gradually turns into stiffness
Difficulty controlling hand movements
Dramatic reduction of stomach acid production, which leads to the increase of a hormone in the blood called gastrin
Anemia

Patients with atypical mucolipidosis IV usually have mild movement delays, but may be able to walk and speak. They also tend to have milder eye abnormalities, as well as the underproduction of stomach acid seen in the typical form. Rarely, patients may only have the eye abnormality with no brain issues.

What causes mucolipidosis type IV?

Mucolipidosis type IV is caused by a mutation in the gene MCOLN1, which makes the protein mucolipin-1. This protein is believed to influence the movement of fats and proteins across cell membranes. When there is a deficiency in the protein, materials aren’t moved, which causes them to accumulate. This eventually affects various tissue functions, likely causing symptoms. To learn more about how the mucolipidoses are caused and inherited, click here.

How is Mucolipidosis type IV diagnosed?

Mucolipidosis type IV is diagnosed using the following procedures:

Thorough clinical examination
Recording of patient history
Testing for high levels of gastrin in the blood (which is elevated because of the lack of stomach acid being produced)
Examination of tissues that reveal cells with numerous inclusion bodies (masses of waste products that accumulate during this disease)
Brain MRIs
Genetic testing

What are the treatments for mucolipidosis type IV?

Mucolipidosis type IV treatment is supportive and catered to the symptoms of each individual patient. It includes:

Physical, occupational, and speech therapy
Nutritional supplements, especially iron and vitamin B12
Use of contact lenses and/or artificial tears to treat clouding of the corneas
Genetic counseling

Where can I find out more about mucolipidosis type IV?