CARDIAC MANIFESTATIONS IN A CHILD WITH A NOVEL MUTATION IN CREATINE TRANSPORTER GENE SLC6A8

Abstract

The creatine-phosphocreatine shuttle serves to maintain a high-energy phosphate supply for normal cellular function. Most creatine is derived from the diet; the rest is synthesized primarily in the liver, pancreas, and kidneys. The transport of creatine in tissues is accomplished by the Na+-dependent transporter SLC6A8. Expression of the SLC6A8 gene is high in skeletal muscle, heart, and kidney, moderate in brain, and extremely low in liver and pancreas. X-linked creatine transporter (Crt) defect (OMIM 300352), originally described in 2001,1 has been linked to mutations in the SL6CA8 gene at Xq28. SLC6A8 deficiency may comprise up to 1% of cases of mental retardation of unknown etiology in males.2 Intellectual disability is the uniform feature in patients with creatine-deficiency syndromes.3,4 Some patients also have epilepsy, extrapyramidal movement disorder, failure to thrive, and sometimes autism and other behavioral problems.4 We report a novel mutation in the SLC6A8 gene in an 11-year-old boy with Crt defect, who presented with multiple premature ventricular contractions (PVCs) in the second year of life. ### Case report. This male child had poor weight gain since birth. By 18 months of age his weight dropped below the fifth percentile and he was admitted for investigation. When given midazolam IV and topical lidocaine before an endoscopy, he immediately developed frequent PVCs (bigeminy …