Epilepsy Research 150 (2019) 70–77 Contents lists available at ScienceDirect Epilepsy Research journal homepage: www.elsevier.com/locate/epilepsyres Genetic testing in a cohort of patients with potential epilepsy with myoclonic-atonic seizures T ⁎ Katie Angione , Krista Eschbach, Garnett Smith, Charuta Joshi, Scott Demarest University of Colorado Denver, Department of Pediatrics, Section of Neurology, United States ARTICLE INFO ABSTRACT Keywords: Epilepsy with myoclonic-atonic seizures (EMAS) accounts for 1–2% of all childhood-onset epilepsies. EMAS has Epilepsy been shown to have an underlying genetic component, however the genetics of this disorder is not yet well Myoclonic atonic understood. The purpose of this study was to review genetic testing results for a cohort of EMAS patients. A Doose retrospective chart review was conducted for 77 patients evaluated at Children’s Hospital Colorado with a po- Genetics tential diagnosis of EMAS. Genetic testing and biochemical testing was reviewed. Family history data was also collected. Seventy-seven percent of the cohort had at least one genetic test performed, and a molecular diagnosis was reached for six patients. Thirty-seven patients had a microarray, six of which identified a copy number variant. Only one was felt to contribute to the phenotype (2p16.3 deletion including NRXN1). Fifty-one patients had an epilepsy panel, two of which were positive (likely pathogenic variant in SCN1A, pathogenic variant in GABRG2). Of the six patients who had whole exome sequencing, two were negative, three were positive or likely positive, and one had multiple variants not felt to explain the phenotype. While EMAS is widely accepted to have a strong genetic component, the diagnostic yield of genetic testing remains low. This may be because several genes now thought to be associated with EMAS are not included on the more commonly ordered epilepsy panels, or have only recently been added to them. 1. Introduction polygenic in some cases Kelley and Kossoff, 2010; Doose et al., 1970; Tang and Pal, 2012. This has complicated the identification of clear Epilepsy with myoclonic-atonic seizures (EMAS), also known as genetic etiologies. While several genes have been associated with Doose syndrome, is an epilepsy syndrome accounting for one to two EMAS, (including SCN1A (Ebach et al., 2005; Escayg et al., 2001), percent of all childhood-onset epilepsies (Kelley and Kossoff, 2010). SCN1B (Kelley and Kossoff, 2010; Scheffer et al., 2001; Wallace et al., EMAS is characterized by multiple seizure types with onset typically 1998), SCN2A Scheffer et al., 2001; Sugawara et al., 2001; Wolff et al., between one and five years of life (Kelley and Kossoff, 2010). Devel- 2017), GABRG2 ( Kelley and Kossoff, 2010; Scheffer et al., 2001; Kang opment is usually normal prior to seizure onset, with a subsequent and Macdonald, 2016), CHD2 (Meller et al., 2017), STX1B (Vlaskamp plateau or regression in most patients. et al., 2016), SLC2A1 (Larsen et al., 2015; Mullen et al., 2011), SLC6A1 Since first described by Dr. Hermann Doose in 1970, the disorder (Carvill et al., 2015; Johnannesen et al., 2018), and GABRB3 (Meller has been felt to have an underlying genetic component given the high et al., 2017)), analysis of these genes in previously reported EMAS prevalence of epilepsy and EEG abnormalities among family members cohorts has yielded positive results in a minority of patients, suggesting of affected individuals. In Doose’s original cohort of 117 patients with that the genetics of EMAS remains poorly understood. The purpose of EMAS, 32% had a positive family history of seizures, while 68–80% had this study is to assess the testing practices and diagnostic yield of a family history of abnormal EEG findings (Kelley and Kossoff, 2010; clinical genetic evaluations in patients with a potential diagnosis of Doose et al., 1970). However, the prevalence of myoclonic or atonic EMAS at a tertiary epilepsy center, as well as to review the existing seizures among family members was much lower (about two percent), literature regarding genetic associations with EMAS. suggesting significant phenotypic variability within affected families (Kelley and Kossoff, 2010; Doose et al., 1970). 2. Material and methods The variability of presentation among individuals with EMAS and their family members suggests that inheritance may be multifactorial or A retrospective chart review was conducted at Children’s Hospital ⁎ Corresponding author at: 13123 E 16th Avenue, B155, Aurora, CO, 80045, United States. E-mail address: [email protected] (K. Angione). https://doi.org/10.1016/j.eplepsyres.2019.01.008 Received 4 September 2018; Received in revised form 10 January 2019; Accepted 13 January 2019 Available online 14 January 2019 0920-1211/ © 2019 Elsevier B.V. All rights reserved. K. Angione et al. Epilepsy Research 150 (2019) 70–77 Colorado. Patients were identified from a clinical database of patients with a potential diagnosis of EMAS. The database included children with epilepsy onset between May 2004 and April 2017. Eligibility cri- teria included consideration of a diagnosis of EMAS by a child neu- rology faculty member at any point in the patient’s course. A definitive diagnosis of EMAS was not required. Patients were excluded if on de- tailed review they never had any clinical or electrographic evidence of drop seizures. Drop seizures were defined as a brief, sudden event that could cause the patient to fall. Additionally, patients were excluded if they had a clear structural etiology on imaging. The cohort was defined by these clinically relevant parameters as evolution of individual pa- tient phenotype over time can result in diagnosis switching and delay in final diagnosis (Eschbach et al., 2018), yet genetic testing may already be completed prior to this time. The full electroclinical spectrum of this cohort and diagnosis switching is described in detail in the initial Fig. 1. Results of biochemical and genetic testing for patients with suspected publication on this cohort (Eschbach et al., 2018). Genetic testing was EMAS. Black represents the percentage of patients with positive (abnormal) test results, dark gray represents patients with variants of uncertain significance, reviewed, including chromosomal microarray, mitochondrial DNA and light gray represents patients with normal testing. analysis, single gene testing, epilepsy panels, and whole exome se- quencing (WES). Overall percentage of the cohort tested for key genes previously associated with EMAS (SCN1A, SCN1B, SCN2A, GABRG2, analyzed ranging from 38 – 89. This variability depended on the type of CHD2, STX1B, SLC2A1, SLC6A1, and GABRB3) through any form of epilepsy panel ordered and date of testing. Some of these panels have testing was noted. For variants of uncertain significance (VUS), results been updated over time as new genes have been discovered (including of parental testing were also noted. Results of panel testing were con- several genes with a proposed association with EMAS), so the presence sidered “normal” if completely negative, or if all variants were identi- or absence of these genes was noted for each patient’s panel. Overall, 51 fied in a heterozygous state in an autosomal recessive gene, in which patients (66%) had an epilepsy panel. Thirty-nine of these (76.5%) case they would not be expected to be clinically relevant. were normal, including 24 negative panels and 15 with one or more Pertinent biochemical testing was also reviewed to identify any heterozygous variants in autosomal recessive genes. Ten patients metabolic abnormalities and to assess the utility of this testing in an (19.6%) had variants of uncertain significance in autosomal dominant EMAS cohort. This included 3-methylglutaconic acid, acylcarnitine, genes, including three in the GABRG2 gene, which has previously been serum amino acids, ammonia, glucose, lactate, pyruvic acid, very long associated with EMAS. Of the GABRG2 variants identified, two were chain fatty acids, urine organic acids, and cerebrospinal fluid studies inherited from asymptomatic fathers and the inheritance is unknown (amino acids, glucose, BH4/neopterin, folate/5MTHF, neuro- for the other. Specifics of these patients’ clinical presentations are transmitters, protein, and pyridoxal-5-phosphate). shown in Table 1B. The remaining seven patients had variants which Family history data was collected to determine the prevalence of were inherited from an asymptomatic parent and /or were inconsistent epilepsy family history in the cohort and to assess whether familial with the patient’s clinical presentation (Supplemental Table 1). Two variants had been inherited from symptomatic or asymptomatic in- patients (4%) were found to have pathogenic variants, one in the dividuals. Family history was specifically reviewed for childhood onset SCN1A gene and one in the GABRG2 gene, both of which have pre- epilepsy, febrile seizures, intellectual disability, and autism, and any viously been associated with EMAS. The overall yield of genetic testing other relevant neurodevelopmental history was also noted. All data in this cohort for the genes most commonly associated with EMAS is analyses were descriptive in nature using frequencies and percentages. shown in Fig. 2. This study was reviewed and approved by the University of Colorado Of the six patients who had whole exome sequencing, two were Multiple Institutional Review Board (COMIRB) with waiver of consent. negative and one had variants of uncertain significance in NIPA1, SZT2, and FAH. Three patients had abnormal findings which were felt to at 3. Results least partially explain their symptoms, including a de novo pathogenic variant in CHD2,ade novo likely pathogenic variant in CSNK2A1, and The cohort consisted of 77 patients with a suspected diagnosis of compound heterozygous variants in PIGN. EMAS, including 19 females (25%) and 58 males (75%). As described in Of the 72 patients (93.5%) who had biochemical testing, only one the earlier publication regarding this cohort, 50 patients (65%) had a (1.4%) had abnormal results significant enough to prompt additional change in epilepsy diagnosis over time and 57 patients (74%) had a studies, which was an elevation of 3-methylglutaconic acid.