Mucopolysarcharidosis Type VII (MPS VII)

Mucopolysarcharidosis type VII (MPS VII) is a rare, inherited disorder. It is classified as a lysosomal storage disorder (LSD), in which a genetic variation disrupts the normal activity of lysosomes in human cells. MPS VII is also known as Sly syndrome.

Lysosomes contain specific proteins (enzymes) 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 proper cell function.

Symptoms of MPS VII fall on a broad spectrum, and the severity and number of symptoms varies widely among individuals. The most severe form of MPS VII leads to a condition known as hydrops fetalis in which excess fluid accumulates in the body’s tissues before birth. Children with hydrops fetalis are often stillborn or die shortly after birth. Symptoms of less severe forms of MPS VII may appear during early childhood.

Signs and symptoms may include:

• An enlarged head (macrocephaly)
• Build-up of fluid in the brain (hydrocephalus)
• An enlarged tongue (macroglossia)
• Coarse facial features
• Umbilical hernia or inguinal hernia
• Arthritis
• Carpal tunnel syndrome
• Joint contractures or deformities
• Short stature

Other symptoms children might experience over time include:

• Sleep apnea
• Hearing loss
• Visual impairment/corneal clouding
• Enlarged liver and spleen (hepatosplenomegaly)
• Thickening of the heart valves
• Compression of the spinal cord
• Frequent respiratory infections
• Intellectual or developmental disability

MPS VII is caused by a deficiency in an enzyme known as beta-glucaronidase. The condition is genetic and inherited in an autosomal recessive pattern. This means that an affected child has received one defective copy of the gene responsible for beta-glucaronidase production from each of their parents.

Current approaches to MPS VII are tailored to specific patients and may include enzyme replacement therapy (ERT) and targeted symptom management. Treatment plans require interdisciplinary collaboration and depend greatly on how the disease is affecting the child.

At the Boston Children’s Lysosomal Storage Disorder (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 MPS VII.