Phenotypic and Molecular Spectrum of Guanidinoacetate N-Methyltransferase Deficiency: An Analytical Study of a Case Series and a Scoping Review of 53 Cases of Guanidinoacetate N-Methyltransferase.

Background: Guanidinoacetate methyltransferase deficiency (GAMT) is an autosomal recessive inborn error of metabolism. A condition that results from a pathogenic variant in the GAMT gene that maps to 19p13.3. The prevalence can be estimated to be up to 1:2,640,000 cases; countries such as Saudi Arabia could have a higher prevalence due to high consanguinity rates. The clinical manifestations that a patient could obtain are broad and start to manifest in the patients' early childhood years. Materials and Methods: A thorough review of case reports in January 2022 was conducted. The retrieved literature was screened for demographic data. Patients of all ages were included. Qualitative variables were described as number and percentage (%), and quantitative data were described by the mean and standard deviation. In bivariate data, Chi-square test (χ2) was used and t-test for nonparametric variables. Results: Gender distribution was 53% of males and 47% females. Reported age ranged from 8 to 31 months. At the age of onset, 50% of the cases were infants, 28% were toddlers, and 15% were children, concluding that 79% of the reported cases developed symptoms before 5 years old. 68% of the cases developed generalized seizures throughout their life. 84% of the cases expressed a form of developmental delay. 43% of the cases had intellectual disabilities and mental retardation that affected their learning process; most cases required special care. 23% of the affected cases were of consanguineous marriages, and 7% had affected relatives. Conclusion: We described four novel case reports, the first to be reported in Saudi Arabia. Seizure was a leading finding in the majority of the cases. Developmental delay was broadly observed. Intellectual delay and language impairments are primary hallmarks. Further understanding and early diagnosis are recommended. Premarital testing of neurogenetic diseases using whole-exome sequencing is probably a future direction, especially in populations with high consanguinity rates.

Current Concepts in the Management of Sanfilippo Syndrome (MPS III): A Narrative Review.

Sanfilippo syndrome is a childhood-onset (1-4 years) autosomal recessive lysosomal storage disease that presents as a neurodegenerative disease by targeting the brain and spinal cord. It is also known as mucopolysaccharidosis III. Mucopolysaccharidosis III is divided into four subtypes (A, B, C, or D). It can cause delayed speech, behavior problems, and features of autism spectrum disorder. Sanfilippo syndrome is of a higher prevalence within consanguineous families that carry its gene alteration. If both parents have a nonfunctional copy of a gene linked to this condition, their children will have a 25% (1 in 4) chance of developing the disease. In Saudi Arabia, the incidence rate is estimated at 2 per 100,000 live births. Recent research focused on promising treatment approaches, such as gene therapy, modified enzyme replacement therapy, and stem cells. These approaches work by exogenous administration of the proper version of the mutant enzyme (enzyme replacement therapy), cleaning the defective enzyme in individuals with glycolipid storage disorders (substrate reduction therapy), or using a pharmacological chaperone to target improperly folded proteins. However, there is currently no approved curative medication for Sanfilippo syndrome that can effectively halt or reverse the disorder.