Case Series of Creatine Deficiency Syndrome due to Guanidinoacetate Methyltransferase Deficiency

Guanidinoacetate N-methyltransferase deficiency: Case report and brief review of the literature

Guanidinoacetate N-methyltransferase (GAMT) deficiency is a rare autosomal recessive disorder characterized by a decrease in creatine synthesis, resulting in cerebral creatine deficiency syndrome (CCDS). GAMT deficiency is caused by mutations in the GAMT gene located on chromosome 19, which impairs the conversion of guanidinoacetic acid (GAA) to creatine. The resulting accumulation of the toxic metabolite GAA and the lack of creatine lead to various symptoms, including global developmental delays, behavioral issues, and epilepsy. The gold standard for diagnosis of GAMT deficiency is genetic testing. Treatment options for GAMT deficiency include creatine supplementation, ornithine supplementation, arginine restriction, and sodium benzoate supplementation. These treatment options have been shown to improve movement disorders and epileptic symptoms, but their impact on intellectual and speech development is limited. Early intervention has shown promising results in normalizing neurological development in a minor subgroup of patients. Therefore, there is a growing need for newborn screening techniques to detect GAMT deficiency early and prevent permanent neurological delays. Here we report a case of GAMT deficiency with emphasis on imaging presentation. Our case showed reduced brain parenchyma creatine stores on MR Spectroscopy, which may provide an avenue to aid in early diagnosis.

Intellectual Disability and Brain Creatine Deficit: Phenotyping of the Genetic Mouse Model for GAMT Deficiency

Guanidinoacetate methyltransferase deficiency (GAMT-D) is one of three cerebral creatine (Cr) deficiency syndromes due to pathogenic variants in the GAMT gene (19p13.3). GAMT-D is characterized by the accumulation of guanidinoacetic acid (GAA) and the depletion of Cr, which result in severe global developmental delay (and intellectual disability), movement disorder, and epilepsy. The GAMT knockout (KO) mouse model presents biochemical alterations in bodily fluids, the brain, and muscles, including increased GAA and decreased Cr and creatinine (Crn) levels, which are similar to those observed in humans. At the behavioral level, only limited and mild alterations have been reported, with a large part of analyzed behaviors being unaffected in GAMT KO as compared with wild-type mice. At the cerebral level, decreased Cr and Crn and increased GAA and other guanidine compound levels have been observed. Nevertheless, the effects of Cr deficiency and GAA accumulation on many neurochemical, morphological, and molecular processes have not yet been explored. In this review, we summarize data regarding behavioral and cerebral GAMT KO phenotypes, and focus on uncharted behavioral alterations that are comparable with the clinical symptoms reported in GAMT-D patients, including intellectual disability, poor speech, and autistic-like behaviors, as well as unexplored Cr-induced cerebral alterations.

Genetic Testing in Various Neurodevelopmental Disorders Which Manifest as Cerebral Palsy: A Case Study From Iran

Purpose: Cerebral palsy (CP) is a heterogeneous permanent disorder impacting movement and posture. Investigations aimed at diagnosing this disorder are expensive and time-consuming and can eventually inconclusive. This study aimed to determine the diagnostic yield of next generation sequencing in patients with atypical CP (ACP). Methods: Patient eligibility criteria included impaired motor function with onset at birth or within the first year of life, and one or more of the following conditions: severe intellectual disability, positive family history, brain imaging findings not typical for cerebral palsy, abnormal neurometabolic profile, intractable seizure, normal neuroimaging despite severe psychomotor disability, after pediatric neurologist assessment including neuroimaging and biochemical-metabolic study offered for genetic study. Results: Exome sequencing was done for 66 patients which revealed pathogenic, likely pathogenic, and variants of unknown significance in 36.2, 9, and 43.9%, respectively. We also found 10 new mutations and were able to suggest specific and personalized treatments for nine patients. We also found three different mutations with different phenotypical spectrum in one gene that have not been reported for cerebral palsy. Conclusion: An accurate history and physical examination and determination of patients with atypical cerebral palsy for doing exome sequencing result in improved genetic counseling and personalized management.