Two novel ECHS1 variants, affecting splicing and reducing enzyme activity, is associated with mitochondrial encephalopathy in infant: a case report

A Case of ECHS1 Deficiency with Severe Encephalopathy and Status Epilepticus after a Propofol Sedation: Case Report

BACKGROUND

Short-chain enoyl-CoA hydratase (ECHS1) deficiency is a rare metabolic disorder. Concerned patients present with Leigh syndrome symptoms or a Leigh-like syndrome. Only 58 patients are known worldwide. The ECHS1 is a key component in β-oxidation and valine catabolic pathways.

CASE

Here we report a 6-month-old Lebanese boy born to consanguineous parents. He presented an increased muscle tone, hyperexcitability, feeding problems, horizontal nystagmus, and developmental delay. Magnetic resonance imaging of the brain revealed frontal brain atrophy, corpus callosum atrophy, and T2 hyperintensity in pallidum, internal capsule, pons, and thalamus. In the postsedation phase, the patient displayed a sudden generalized seizure with transition to status epilepticus. Therefore, we conducted metabolic examinations, which showed elevated levels of 2-methyl-2,3-DiOH-butyrate and 3-methylglutaconate in urine. Single exome sequencing revealed the homozygous mutation c.476A > G in the ECHS1 gene.

CONCLUSION

This case report describes the clinical symptoms and the diagnostics of ECHS1 deficiency. It shows the importance of further metabolic and genetic testing of patients with motoric conspicuities and developmental delay. It is important to be cautious with propofol sedation of patients who present an unknown neurological disorder, when metabolic disturbance or especially mitochondriopathy is suspected.

Whole-exome sequencing identified novel variants in three Chinese Leigh syndrome pedigrees

Leigh syndrome (LS), the most common mitochondrial disease in early childhood, usually manifests variable neurodegenerative symptoms and typical brain magnetic resonance imaging (MRI) lesions. To date, pathogenic variants in more than 80 genes have been identified. However, there are still many cases without molecular diagnoses, and thus more disease-causing variants need to be unveiled. Here, we presented three clinically suspected LS patients manifesting neurological symptoms including developmental delay, hypotonia, and epilepsy during the first year of age, along with symmetric brain lesions on MRI. We explored disease-associated variants in patients and their nonconsanguineous parents by whole-exome sequencing and subsequent Sanger sequencing verification. Sequencing data revealed three pairs of disease-associated compound heterozygous variants: c.1A>G (p.Met1?) and 409G>C (p.Asp137His) in SDHA, c.1253G>A (p.Arg418His) and 1300C>T (p.Leu434Phe) in NARS2, and c.5C>T (p.Ala2Val) and 773T>G (p.Leu258Trp) in ECHS1. Among them, the likely pathogenic variants c.409G>C (p.Asp137His) in SDHA, c.1300C>T (p.Leu434Phe) in NARS2, and c.773T>G (p.Leu258Trp) in ECHS1 were newly identified. Segregation analysis indicated the possible disease-causing nature of the novel variants. In silico prediction and three-dimensional protein modeling further suggested the potential pathogenicity of these variants. Our discovery of novel variants expands the gene variant spectrum of LS and provides novel evidence for genetic counseling.

Exploring triheptanoin as treatment for short chain enoyl CoA hydratase deficiency

We explored the benefits of triheptanoin as a treatment for Short Chain Enoyl Co‐A Hydratase (SCEH) deficiency. One child with early onset, severe SCEH Deficiency was treated with triheptanoin, an odd chain oil with anapleurotic properties, for 37 months. Blood and urine chemistry safety measures, motor skills assessment, physical exam, and neurological assessment were monitored over a 27 month period. Modest sustained gains in motor skills, attention, muscle bulk, and strength were observed without any significant adverse effects. Triheptanoin appears to be a promising effective treatment for SCEH Deficiency.

ECHS1 disease in two unrelated families of Samoan descent: Common variant - rare disorder

Mutations in the short-chain enoyl-CoA hydratase (SCEH) gene, ECHS1, cause a rare autosomal recessive disorder of valine catabolism. Patients usually present with developmental delay, regression, dystonia, feeding difficulties, and abnormal MRI with bilateral basal ganglia involvement. We present clinical, biochemical, molecular, and functional data for four affected patients from two unrelated families of Samoan descent with identical novel compound heterozygous mutations. Family 1 has three affected boys while Family 2 has an affected daughter, all with clinical and MRI findings of Leigh syndrome and intermittent episodes of acidosis and ketosis. WES identified a single heterozygous variant in ECHS1 at position c.832G > A (p.Ala278Thr). However, western blot revealed significantly reduced ECHS1 protein for all affected family members. Decreased SCEH activity in fibroblasts and a mild increase in marker metabolites in urine further supported ECHS1 as the underlying gene defect. Additional investigations at the DNA (aCGH, WGS) and RNA (qPCR, RT-PCR, RNA-Seq, RNA-Array) level identified a silent, common variant at position c.489G > A (p.Pro163=) as the second mutation. This substitution, present at high frequency in the Samoan population, is associated with decreased levels of normally spliced mRNA. To our understanding, this is the first report of a novel, hypomorphic allele c.489G > A (p.Pro163=), associated with SCEH deficiency.