creatine transporter deficiency

What is Creatine Transporter Deficiency?

Creatine transporter deficiency (CRTR deficiency) is a condition characterized by intellectual disability. It is caused by harmful genetic changes (variants) in the SLC6A8 gene. Individuals with this disorder have symptoms because their body cannot properly use an important substance called creatine. The body needs creatine to produce energy for the brain and muscle cells. Individuals with creatine transporter deficiency cannot move the creatine from their bloodstream into their cells. Because of this, the cells do not have enough energy to function correctly.

CRTR deficiency is an X-linked condition, meaning the SLC6A8 gene is on the X-chromosome. Biological males have one copy of the X-chromosome (XY) and the SLC6A8 gene, while biological females have two copies (XX). Because of this, CRTR deficiency primarily affects males, while most female carriers are unaffected. However, some females can have symptoms.

Symptoms in males with CRTR deficiency are typically noticed in infancy or early childhood. The first symptoms are typically a delay in reaching milestones, such as learning to crawl, walk, or speak. All males with this disorder have an intellectual disability. Some may have other symptoms, including behavioral issues such as autistic features or attention deficit hyperactivity disorder (ADHD), low muscle tone (hypotonia), abnormal movements, digestive problems, distinct facial features, and heart problems.

Additional considerations for carriers

Some females with a harmful genetic change in SLC6A8 have intellectual disability that is milder than what is seen in males. Others do not have any symptoms of the disorder. In rare cases, females have symptoms that are similar in severity to males.

How common is Creatine Transporter Deficiency?

The exact incidence of CRTR deficiency is unknown. Approximately 150 individuals have been diagnosed worldwide.

How is Creatine Transporter Deficiency treated?

There is no cure for CRTR deficiency. Individuals can take creatine and other nutritional supplements by mouth, leading to symptom improvement in some but not all people with the disorder. Other treatments are directed at managing the specific symptoms an individual has. Individuals diagnosed with CRTR deficiency will often benefit from receiving speech, physical, occupational, and behavioral therapies and other supportive services beginning at a young age. Medications may be used to manage seizures, behavioral issues, and abnormal movements.

What is the prognosis for an individual with Creatine Transporter Deficiency?

The prognosis depends on the severity of an individual’s symptoms. Reports of males with CRTR living into their sixties indicate that a normal life expectancy is possible. All males with CRTR deficiency are expected to have an intellectual disability. Many cannot speak in complete sentences and need help with activities of daily living, such as dressing and feeding. They are not usually able to live independently.