Case Report: Clinical and Magnetic Resonance Spectroscopy Presentation of a Female Severely Affected with X-linked Creatine Transporter Deficiency

Creatine transporter deficiency is an X-linked genetic disorder caused by a variant in the SLC6A8 gene located on the X chromosome (Xq28). This condition varies in severity with features often including intellectual disabilities, speech delay, autistic features, attention deficit hyperactivity and gastrointestinal issues. While creatine transporter deficiency primarily affects males, females may also demonstrate severe phenotypes. However, screening of creatine transporter deficiency in females can be especially difficult as urine creatine/creatinine screenings often have values falling within normative ranges. Also, females may not demonstrate the characteristic reduction of creatine concentrations in the brain visualized with in vivo proton magnetic resonance spectroscopy. Identification typically results from exome sequencing. In this report, we present the clinical, imaging, and spectroscopy features of a heterozygous female with a severe presentation of creatine transporter deficiency.