Why Do Children With MPS I Get Carpal Tunnel Syndrome?

In adults, carpal tunnel syndrome is a common condition typically caused by repetitive motion or wear-and-tear. However, in children under the age of 10, carpal tunnel syndrome is extremely rare and is considered a major clinical red flag ^[1]. When a young child develops carpal tunnel syndrome without an obvious physical cause, it is highly indicative of an underlying systemic condition, such as a metabolic disorder like Mucopolysaccharidosis type I (MPS I) or other genetic and inflammatory conditions ^[2][1].

In children with MPS I, carpal tunnel syndrome is not caused by repetitive strain. Instead, it is caused by the continuous buildup of complex sugar molecules called glycosaminoglycans (GAGs) that thicken the connective tissues in the wrist and compress the nerve ^[3][4].

How MPS I Causes Carpal Tunnel Syndrome

The carpal tunnel is a narrow passageway in the wrist, roofed by a band of connective tissue called the flexor retinaculum, which protects the median nerve and tendons.

In MPS I, a missing or deficient enzyme prevents the body from breaking down GAGs. Over time, these GAGs accumulate in cells throughout the body ^[3]. When GAGs build up in the wrist, the flexor retinaculum and surrounding connective tissues become significantly thicker ^[4]. Because the carpal tunnel is a rigid space that cannot expand, this thickened tissue presses directly on the median nerve, leading to nerve compression and damage ^[4].

Why It Is a Crucial Warning Sign

Because children do not have decades of repetitive stress on their wrists, standard carpal tunnel syndrome is practically unheard of in the general pediatric population ^[1]. If a young child exhibits symptoms of median nerve compression, it should immediately prompt a physician to screen for a lysosomal storage disease like MPS I ^[4].

In milder (attenuated) forms of MPS I—such as Scheie syndrome—carpal tunnel syndrome can actually be the very first recognized clinical symptom ^[5]. Research shows that in some patients with attenuated MPS I, carpal tunnel syndrome is diagnosed an average of 7.5 years before the underlying genetic condition is officially identified ^[4]. For families who have spent years seeking answers for their child’s unexplained symptoms, learning this connection can be both validating and overwhelming. Recognizing this red flag early is critical, as timely diagnosis and metabolic therapy can significantly improve the child’s overall long-term prognosis ^[6].

Signs of Carpal Tunnel in Children

Diagnosing carpal tunnel syndrome in children can be challenging, often leading to diagnostic delays ^[7]. Children may not be able to articulate classic symptoms like “tingling” or “numbness” in their fingers. Instead, parents and doctors should watch for:

• Loss of dexterity: Trouble holding a pencil, buttoning shirts, or picking up small objects.
• Unusual clumsiness: Dropping items frequently.
• Hand pain or night waking: Waking up in the middle of the night crying, shaking, or rubbing their hands.
• Muscle wasting: A noticeable flattening or loss of muscle at the base of the thumb (known as thenar hypoplasia) ^[8].

If you notice these signs in your child, bring them to a pediatrician or pediatric neurologist and mention your concerns about underlying metabolic conditions.

Monitoring and Treatment

Importantly, even if a child is receiving treatments like enzyme replacement therapy (ERT) or a stem cell transplant for MPS I, these treatments do not always prevent or fully reverse the buildup of GAGs in the wrist ^[4]. Therefore, regular monitoring of nerve function is essential. This is typically done using nerve conduction studies (NCS)—a test that measures how fast electrical signals move through the nerve—or a specialized wrist ultrasound ^[8].

When compression is confirmed, carpal tunnel release surgery is often required to relieve the pressure and preserve the child’s hand strength and function ^[3][9]. Unlike in adults, this surgery for young children is usually performed under general anesthesia. It involves cutting the thickened flexor retinaculum to create more space for the median nerve, preventing permanent nerve damage and preserving quality of life ^[9].