About MPS IIIB

A simple guide for parents and caregivers.

MPS IIIB stands for Mucopolysaccharidosis Type IIIB. It is also called Sanfilippo Syndrome Type B. It is a rare genetic disease that mostly affects the brain and the nervous system.

Children with MPS IIIB are missing enough of an enzyme called NAGLU. This enzyme helps the body break down a sugar molecule called heparan sulfate. Without enough NAGLU, this sugar builds up in the cells of the brain and other parts of the body. Over time, this buildup can damage brain cells.

How MPS IIIB affects children

What families often see

MPS IIIB usually starts to show in early childhood. Each child is different. But many families notice some of the same things over time:

Slower learning of new skills, like speech and play
A loss of skills the child once had
Trouble sleeping or changes in sleep
Big changes in mood or behavior, like more activity or trouble sitting still
Seizures, in some children
Changes in walking, eating, or moving over time

MPS IIIB is a progressive disease. That means symptoms tend to get worse over time. Right now, there is no approved medicine that treats the cause of MPS IIIB. Care today focuses on helping with symptoms and supporting the whole family.

A genetic condition

MPS IIIB is genetic. A child gets it when they receive a changed copy of the NAGLU (N-acetyl-alpha-glucosaminidase) gene from each parent. Most parents are carriers and have no signs of the disease themselves. Many families have no idea MPS IIIB is in their family until a child is diagnosed.

A genetic counselor can help your family understand testing, results, and what they mean for siblings or future children.

Support and resources

A diagnosis of MPS IIIB can feel overwhelming. Many parents tell us they wish they had known sooner that other families were going through the same thing. There are patient groups and support communities for MPS IIIB families.

Cure Sanfilippo Foundation

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National MPS Society

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A Clinical Study and Expanded Access Program for Children with MPS IIIB

Spruce Biosciences is sponsoring two related opportunities for people with MPS IIIB. They are not the same. One is a clinical study, and the other is an Expanded Access Program (EAP). The right one for your child depends on participant’s age, their care needs, where you live, and other factors.

See Who Is Eligable