X-linked creatine transporter (SLC6A8) deficiency in females: Difficult to recognize, but a potentially treatable disease.

Abstract

Creatine transporter deficiency (CTD), caused by pathogenic variants in SLC6A8, is the second most common cause of X-linked intellectual disability. Symptoms include intellectual disability, epilepsy, and behavioral disorders and are caused by reduced cerebral creatine levels. Targeted treatment with oral supplementation is available, however the treatment efficacy is still being investigated. There are clinical and theoretical indications that heterozygous females with CTD respond better to supplementation treatment than hemizygous males. Unfortunately, heterozygous females with CTD often have more subtle and uncharacteristic clinical and biochemical phenotypes, rendering diagnosis more difficult. We report a new female case who presented with learning disabilities and seizures. After determining the diagnosis with molecular genetic testing confirmed by proton magnetic resonance spectroscopy (1H-MRS), the patient was treated with supplementation treatment including creatine, arginine, and glycine. After 28 months of treatment, the patient showed prominent clinical improvement and increased creatine levels in the brain. Furthermore, we provide a review of the 32 female cases reported in the current literature including a description of phenotypes, genotypes, diagnostic approaches, and effects of supplementation treatment. Based on this, we find that supplementation treatment should be tested in heterozygous female patients with CTD, and a prospective treatment underlines the importance of diagnosing these patients. The diagnosis should be suspected in a broad clinical spectrum of female patients and can only be made by molecular genetic testing. 1H-MRS of cerebral creatine levels is essential for establishing the diagnosis in females, and especially valuable when assessing variants of unknown significance.

• Authors: Malene Mejdahl Nielsen, Esben Thade Petersen, Christina Dühring Fenger, Mette Cathrine Ørngreen, Hartwig Roman Siebner, Vincent Oltman Boer, Michal Považan, Allan Lund, Sabine Weller Grønborg, Trine Bjørg Hammer
• Journal: Molecular genetics and metabolism (Mol Genet Metab) Vol. 140 Issue 3 Pg. 107694 (11 2023) ISSN: 1096-7206 [Electronic] United States
• PMID: 37708665 (Publication Type: Journal Article, Review, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.

Chemical References

• creatine transporter
• Creatine
• Plasma Membrane Neurotransmitter Transport Proteins
• SLC6A8 protein, human
• Nerve Tissue Proteins

Topics

• Male
• Humans
• Female
• Intellectual Disability (genetics)
• Creatine
• Brain Diseases, Metabolic, Inborn (diagnosis, genetics, drug therapy)
• Mental Retardation, X-Linked (diagnosis, genetics)
• Plasma Membrane Neurotransmitter Transport Proteins (genetics)
• Nerve Tissue Proteins