Creatine transporter deficiency (CRTR deficiency) is a condition that causes intellectual disability. People with CRTR deficiency cannot move creatine from their blood into their cells, so their cells do not get enough energy to work properly.
Symptoms in males usually start in infancy or early childhood. The first signs are often delays in milestones like crawling, walking, or talking. All males with this disorder have intellectual disabilities. They may also have other symptoms like behavioral issues (such as autism or ADHD), low muscle tone, abnormal movements, digestive problems, distinct facial features, and heart problems. There is no cure for CRTR deficiency, but taking creatine and other supplements might help some people. Treatment focuses on managing specific symptoms. This can include speech, physical, occupational, and behavioral therapies, as well as medications to help with seizures, behavior, and movement issues. Starting these supportive services early can be very beneficial.
CRTR deficiency is caused by pathogenic variants in the SLC6A8 gene and exhibits X-linked recessive inheritance. This means that one pathogenic variant is enough to cause the disease in both individuals assigned male at birth (who have one X chromosome and one Y chromosome) and individuals assigned female at birth (who have two X chromosomes) may experience symptoms depending on how many copies of the X chromosome that has the pathogenic variant are turned on in the cells.
Some carrier females have intellectual disability that is milder than what is seen in males. In rare cases, females have symptoms that are similar in severity to males.
Resources:
Association for Creatine Deficiencies
National Organization for Rare Disorders
Written August 2024
