Mucolipidosis I (ML I)

Mucolipidosis I (ML I) is a rare, inherited disorder. Mucolipidosis I is also known as sialidosis. The condition is classified as a lysosomal storage disorder (LSD). In these disorders, genetic variations disrupt the normal activity of lysosomes in human cells. ML I affects many organ systems, including the nervous system.

Lysosomes contain specific proteins (enzymes) that are responsible for breaking down and recycling molecules such as fats and sugars. Individuals with a lysosomal storage disorder lack one of these necessary enzymes or do not have one of these enzymes in sufficient quantities to break down molecules for cells to function properly.

Symptoms of Mucolipidosis I fall on a broad spectrum. A child with the condition may or may not experience symptoms. They may have symptoms as early as birth or not have symptoms until childhood or adolescence. Children who show signs and symptoms of Mucolipidosis I at birth typically have a more severe form of the disease.

Signs and symptoms may include:

• Distinct facial features (coarse facial features)
• Abnormal skeletal development
• Enlargement of the liver and spleen (hepatosplenomegaly)
• Short stature
• Muscle twitching (myoclonus)
• Gait disturbance

Other symptoms children might experience over time include:

• Intellectual disability
• Visual impairment/corneal clouding
• Mobility impairment

Mucolipidosis I is caused by a mutation on the NEU1 gene, resulting in a deficiency in an enzyme known as neuraminidase 1, which lysosomes require to properly break down large sugar molecules inside the body’s cells. This genetic condition is inherited in an autosomal recessive pattern, which means that an affected child has received one defective copy of the NEU1 gene from each of their parents.

There are currently no approved therapies which reverse the effects of Mucolipidosis I. Current approaches involve managing specific symptoms through targeted therapies and collaboration between specialists.

At the Boston Children’s Lysosomal Storage Disorders (BoLD) Program, our team of providers is committed to the care of complex patients. As part of Boston Children’s Hospital, we are prepared to meet the challenge of providing multifaceted care by partnering with you and your child to deliver direct care in our BoLD clinic. We work with the broad array of world-class specialists at Boston Children’s to optimize the care we provide your child with Mucolipidosis I.