Population Prevalence of Deleterious SGCE Variants

Identification of ultra-rare genetic variants in pediatric acute onset neuropsychiatric syndrome (PANS) by exome and whole genome sequencing

Abrupt onset of severe neuropsychiatric symptoms including obsessive-compulsive disorder, tics, anxiety, mood swings, irritability, and restricted eating is described in children with Pediatric Acute-Onset Neuropsychiatric Syndrome (PANS). Symptom onset is often temporally associated with infections, suggesting an underlying autoimmune/autoinflammatory etiology, although direct evidence is often lacking. The pathological mechanisms are likely heterogeneous, but we hypothesize convergence on one or more biological pathways. Consequently, we conducted whole exome sequencing (WES) on a U.S. cohort of 386 cases, and whole genome sequencing (WGS) on ten cases from the European Union who were selected because of severe PANS. We focused on identifying potentially deleterious genetic variants that were de novo or ultra-rare (MAF) < 0.001. Candidate mutations were found in 11 genes (PPM1D, SGCE, PLCG2, NLRC4, CACNA1B, SHANK3, CHK2, GRIN2A, RAG1, GABRG2, and SYNGAP1) in 21 cases, which included two or more unrelated subjects with ultra-rare variants in four genes. These genes converge into two broad functional categories. One regulates peripheral immune responses and microglia (PPM1D, CHK2, NLRC4, RAG1, PLCG2). The other is expressed primarily at neuronal synapses (SHANK3, SYNGAP1, GRIN2A, GABRG2, CACNA1B, SGCE). Mutations in these neuronal genes are also described in autism spectrum disorder and myoclonus-dystonia. In fact, 12/21 cases developed PANS superimposed on a preexisting neurodevelopmental disorder. Genes in both categories are also highly expressed in the enteric nervous system and the choroid plexus. Thus, genetic variation in PANS candidate genes may function by disrupting peripheral and central immune functions, neurotransmission, and/or the blood-CSF/brain barriers following stressors such as infection.

Detection of a new deleterious SGCE gene variant in Moroccan family with inherited myoclonus–dystonia

Myoclonus–dystonia (M‐D) is a pleiotropic neuropsychiatric disorder with autosomal dominant mode of inheritance with variable severity and incomplete penetrance. Pathogenic variants in ξ‐sarcoglycan gene SGCE are the most frequently known genetic cause of M‐D with maternal imprinting, and in most cases, a symptomatic individual inherits the pathogenic variant from his or her father. This work reported a missense mutation c.662G> T inherited in the M‐D Moroccan family described for the first time, which is deleterious based on protein modeling analysis.

A mixed-ethnicity myoclonus-dystonia patient with a novel SGCE nonsense mutation: a case report

Background

Myoclonus-dystonia is a rare movement disorder with an autosomal dominant inheritance pattern characterized by a combination of myoclonic jerks and dystonia that may have psychiatric manifestations. Our aim is to present neurologic and psychiatric phenotypic characteristics in the first Filipino bi-ethnic myoclonus-dystonia patient and her father.

Case presentation

We investigated a Filipino myoclonus-dystonia patient with a positive family history. This 21-year-old woman of mixed Filipino-Greek ethnicity presented with involuntary jerking movements of her upper extremities, head, and trunk. Her symptoms affected her activities of daily living which led her to develop moderate depression, mild to moderate anxiety, and mild obsessive-compulsive disorder (OCD). Her 49-year-old Greek father suffered from adolescence-onset myoclonus-dystonia.

Conclusion

Genetic testing revealed a novel epsilon-sarcoglycan (SGCE) gene nonsense mutation c.821C > A; p.Ser274* that confirmed our clinical diagnosis. For co-morbid anxiety, depression, and OCD, this patient was given duloxetine, in addition to clonazepam for the myoclonus and dystonia.