Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population.

Truncus Arteriosus (TA) is a congenital heart disease characterized by a single common blood vessel emerging from the right and left ventricles instead of the main pulmonary artery and aorta. TA accounts for 4% of all critical congenital heart diseases. The most common cause of TA is 22q11.2 deletion syndrome, accounting for 12-35% of all TA cases. However, no major causes of TA other than 22q11.2 deletion have been reported. We performed whole-genome sequencing of 11 Japanese patients having TA without 22q11.2 deletion. Among five patients, we identified pathogenic variants in TMEM260; the biallelic loss-of-function variants of which have recently been associated with structural heart defects and renal anomalies syndrome (SHDRA). In one patient, we identified a de novo pathogenic variant in GATA6, and in another patient, we identified a de novo probably pathogenic variant in NOTCH1. Notably, we identified a prevalent variant in TMEM260 (ENST00000261556.6), c.1617del (p.Trp539Cysfs*9), in 8/22 alleles among the 11 patients. The c.1617del variant was estimated to occur approximately 23 kiloyears ago. Based on the allele frequency of the c.1617del variant in the Japanese population (0.36%), approximately 26% of Japanese patients afflicted with TA could harbor homozygous c.1617del variants. This study highlights TMEM260, especially c.1617del, as a major genetic cause of TA in the Japanese population.

A Prevalent TMEM260 Deletion Causes Conotruncal Heart Defects, Including Truncus Arteriosus.

Conotruncal heart defects are severe congenital malformations of the outflow tract, including truncus arteriosus (TA) and double-outlet right ventricle (DORV). TA is a severe congenital heart disease (CHD) in which the main arterial outflow tract of the heart fails to separate. We recently reported TMEM260 (NM_017799.4), c.1617del (p.Trp539Cysfs*9), as a major cause of TA in the Japanese population (TMEM260 Keio-Tohoku variant) comparable to the prevalence of the 22q11.2 deletion syndrome, which accounts for 12%-35% of TA. However, no other major causes of TA have not been identified. Here, we report a family that included a TA patient and a DORV patient, harboring the compound heterozygous variants of TMEM260, a 7066-bp deletion encompassing exons 6-7 and c.1393C > T, p.(Gln465*). The allele frequency of the 7066-bp deletion was particularly high in the Japanese population (0.17%). Based on the allele frequency of this deletion and c.1617del (0.36%) in the Japanese population, TMEM260 variants might be associated with more than half of the Japanese patients with TA. This study showed that TMEM260 pathogenic variants might be the most common cause of TA in the Japanese population and could explain the wide spectrum of phenotypes associated with TMEM260-related CHD, including DORV, demonstrating the usefulness of genetic testing in Japanese patients with TA.

Treatment of ZC4H2 Variant-Associated Spastic Paraplegia with Selective Dorsal Rhizotomy and Intensive Postoperative Rehabilitation: A Case Report.

Selective dorsal rhizotomy (SDR) has been used to treat children with spastic cerebral palsy (CP), and its beneficial effect on quality of life and ambulation has been confirmed in long-term follow-up studies. However, the role of SDR in the treatment of spasticity in patients with hereditary spastic paraplegia (HSP) and related disorders is not well-established. Here, we report the first patient with the ZC4H2 variant who underwent SDR to treat spastic paraplegia. Abnormal gait was discovered during a regular checkup at the age of 3 years and 9 months, and she was diagnosed with spastic paraplegia. She was heterozygous for the ZC4H2 variant and underwent SDR at the age of 5 years and 11 months, which alleviated the spasticity. The patient underwent inpatient postoperative rehabilitation for 4 months and continued outpatient physiotherapy after discharge. The Gross Motor Function Measure-88 score and maximum walking speed decreased transiently 1 month postoperatively, but gradually recovered, and continuously improved 6 months postoperatively. SDR and postoperative intensive rehabilitation were effective in improving motor and walking functions up to 6 months after surgery, although long-term follow-up is needed to draw conclusions.

Successful treatment with dimethyl fumarate in a child with relapsing-remitting multiple sclerosis.

INTRODUCTION: Early disease control with disease-modifying drugs is important for improving the prognosis of multiple sclerosis (MS) in children. Dimethyl fumarate (DMF) is an oral disease-modifying drug for MS in adults with relatively stable disease; however, its use in young children has not been heavily documented in the current literature. We report the case of a pediatric patient with relapsing-remitting MS who was treated with DMF. CASE REPORT: A 3-year-old boy with a history of common cold symptoms developed unsteadiness and somnolence. Magnetic resonance imaging revealed multiple white matter lesions. Symptoms were recurrent, and DMF was prescribed at 6 years of age due to a relapse episode with oculomotor disability and facial paralysis. However, disease progression continued, and new lesions were noted at age 7; thus, the dose of DMF was increased to 240 mg/day. No relapse has been observed for over three years; sequelae or severe side effects were absent. CONCLUSIONS: DMF may be a useful oral disease-modifying drug for preventing recurrence in young children with MS.

Two types of early epileptic encephalopathy in a Pitt-Hopkins syndrome patient with a novel TCF4 mutation.

INTRODUCTION: Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder caused by mutations in TCF4. Seizures have been found to vary among patients with PTHS. We report the case of a PTHS patient with a novel missense mutation in the gene TCF4, presenting with two types of early epileptic encephalopathy. CASE REPORT: The patient was a Japanese boy. His first seizure was reported at 17 days of age, with twitching of the left eyelid and tonic-clonic seizures on either side of his body. An ictal electroencephalogram (EEG) showed epileptic discharges arising independently from both hemispheres, occasionally resembling migrating partial seizures of infancy (MPSI) that migrated from one side to the other. Brain magnetic resonance imaging revealed agenesis of the corpus callosum. His facial characteristics included a distinctive upper lip and thickened helices. His seizures were refractory, and psychomotor development was severely delayed. At the age of 10 months, he developed West syndrome with spasms and hypsarrhythmia. After being prescribed topiramate (TPM), his seizures and EEG abnormalities dramatically improved. Also, psychomotor development progressed. Whole-exome sequencing revealed a novel de novo missense mutation in exon 18 (NM_001083962.2:c.1718A > T, p.(Asn573Ile)), corresponding to the basic region of the basic helix-loop-helix domain, which may be a causative gene for epileptic encephalopathy. CONCLUSIONS: To our knowledge, this is the first report of a patient with PTHS treated with TPM, who presented with both MPSI as well as West syndrome. This may help provide new insights regarding the phenotypes caused by mutations in TCF4.