Exploring the Role of FICD, a New Potential Gene Involved in Borderline Intellectual Functioning, Psychological and Metabolic Disorders

Background/Objectives: AMPylation is a post-translational modification involving the transfer of adenosine monophosphate (AMP) from adenosine triphosphate (ATP) to target proteins, serving as a critical regulatory mechanism in cellular functions. This study aimed to expand the phenotypic spectrum associated with mutations in the FICD gene, which encodes an adenyltransferase enzyme involved in both AMPylation and deAMPylation. Methods: A clinical evaluation was conducted on a patient presenting with a complex clinical profile. Whole-exome sequencing (WES) was performed to identify potential genetic variants contributing to the observed phenotype. Results: The patient exhibited borderline intellectual functioning (BIF), acanthosis, abdominal muscle hypotonia, anxiety, depression, obesity, and optic nerve subatrophy. WES revealed a de novo missense variant, c.1295C>T p.Ala432Val, in the FICD gene. This variant, classified as of uncertain significance, is located in the highly conserved region TLLFATTEY (aa 428–436), suggesting a potential impact on protein function. Conclusions: These findings highlight the importance of the FICD gene in diverse clinical manifestations and emphasize the need for further studies to elucidate the genetic mechanisms underlying these phenotypes. Continued research is essential to improve our understanding of FICD-related conditions.