Sunday, January 24, 2021

SLC13A5 deficiency 2

Matricardi S, De Liso P, Freri E, Costa P, Castellotti B, Magri S, Gellera C, Granata T, Musante L, Lesca G, Oertel J, Craiu D, Hammer TB, Møller RS, Barisic N, Abou Jamra R, Polster T, Vigevano F, Marini C. Neonatal developmental and epileptic encephalopathy due to autosomal recessive variants in SLC13A5 gene. Epilepsia. 2020 Nov;61(11):2474-2485. doi: 10.1111/epi.16699. Epub 2020 Oct 16. PMID: 33063863.


Objective: Autosomal recessive pathogenic variants of the SLC13A5 gene are associated with severe neonatal epilepsy, developmental delay, and tooth hypoplasia/hypodontia. We report on 14 additional patients and compare their phenotypic features to previously published patients to identify the clinical hallmarks of this disorder. 

Methods: We collected clinical features of 14 patients carrying biallelic variants in SLC13A5 and performed a PubMed search to identify previously published patients. 

Results: All patients presented clonic or tonic seizures in the first days of life, evolving into status epilepticus in 57%. Analysis of seizure frequency and developmental milestones divided into five epochs showed an evolutionary trajectory of both items. In the first 3 years of life, 72% of patients had weekly/monthly seizures, often triggered by fever; 14% were seizure-free. Between the ages of 3 and 12 years, 60% become seizure-free; in the following years, up to age 18 years, 57% were seizure-free. After the age of 18 years, all three patients reaching this age were seizure-free. Similarly, 86% of patients at onset presented mild to moderate developmental impairment and diffuse hypotonia. In late childhood, all had developmental delay that was severe in most. Benzodiazepines, phenobarbital, phenytoin, and carbamazepine were the most effective drugs. Eight probands carried heterozygous compound variants, and homozygous pathogenic variants occurred in six. Literature review identified 45 patients carrying SLC13A5 gene pathogenic variants whose clinical features overlapped with our cohort. A peculiar and distinguishing sign is the presence of tooth hypoplasia and/or hypodontia in most patients. 

Significance: Autosomal recessive pathogenic variants in SLC13A5 are associated with a distinct neonatal epileptic encephalopathy evolving into severe cognitive and motor impairment, yet with seizures that settle down in late childhood. Tooth hypoplasia or hypodontia remains the peculiar feature. The SLC13A5 gene should be screened in neonatal epileptic encephalopathies; its recessive inheritance has relevance for genetic counseling.

Yang QZ, Spelbrink EM, Nye KL, Hsu ER, Porter BE. Epilepsy and EEG Phenotype of SLC13A5 Citrate Transporter Disorder. Child Neurol Open. 2020 Jun 8;7:2329048X20931361. doi: 10.1177/2329048X20931361. PMID: 32551328; PMCID: PMC7281881.


Mutations in the SLC13A5 gene, a sodium citrate cotransporter, cause a rare autosomal recessive epilepsy (EIEE25) that begins during the neonatal period and is associated with motor and cognitive impairment. Patient's seizure burden, semiology, and electroencephalography (EEG) findings have not been well characterized. Data on 23 patients, 3 months to 29 years of age are reported. Seizures began during the neonatal period in 22 patients. Although seizures are quite severe in many patients later in life, seizure freedom was attainable in a minority of patients. Multiple patients' chronic seizure management included a few common medications, phenobarbital and valproic acid in particular. Patients EEGs had a relatively well-preserved background for age, even in the face of frequent seizures, little slowing and multiple normal EEGs and do not support an epileptic encephalopathy. Other causes for the motor and cognitive delay beyond epilepsy warrant further study. 

Kopel J, Grooms A, Ganapathy V, Clothier J. Metformin, valproic acid, and starvation induce seizures in a patient with partial SLC13A5 deficiency: a case of pharmaco-synergistic heterozygosity. Psychiatr Genet. 2021 Feb 1;31(1):32-35. doi: 10.1097/YPG.0000000000000269. PMID: 33290383.


SLC13A5/NaCT is a sodium-coupled citrate transporter expressed in the plasma membrane of the liver, testis, and brain. In these tissues, SLC13A5 has important functions in the synthesis of fatty acids, cholesterol, and neurotransmitters. In recent years, patients homozygous for recessive mutations in SLC13A5, known as SLC13A5 deficiency [early infantile epileptic encephalopathy-25 (EIEE-25)], exhibit severe global developmental delay, early-onset intractable seizures, spasticity, and amelogenesis imperfecta affecting tooth development. Although the pathogenesis of SLC13A5 deficiency remains not clearly understood, cytoplasmic citrate deficits, decreased energy status in neurons, and citrate-zinc chelation are hypothesized to explain the neurological deficits. However, no study has examined the possibility of specific pharmacological drugs and/or lifestyle changes synergizing with heterozygosity of SLC13A5 deficiency to increase the risk of EIEE-25 clinical phenotype. Here, we report on a heterozygous SLC13A5-deficient patient who demonstrated evidence of pharmaco-synergistic heterozygosity upon administration of metformin, valproic acid, and starvation. The report illustrates the importance of careful consideration of the potential adverse effects of specific pharmacological treatments in patients with heterozygosity for disease-causing recessive mutations in SLC13A5.

Arvio M, Lähdetie J. Adult phenotype of the homozygous missense mutation c.655G>A, p.Gly219Arg in SLC13A5: A case report. Am J Med Genet A. 2020 Nov;182(11):2671-2674. doi: 10.1002/ajmg.a.61802. Epub 2020 Aug 17. PMID: 33200910.


Homozygous recessive or compound heterozygous mutations in SLC13A5-gene as a cause of Early Infantile Epileptic Encephalopathy subtype 25 (OMIM 615905) were published in 2014. Previous clinical reports describe young patients, aged <34 years. We describe 54- and 56-year-old siblings and show that the disorder linked to SLC13A5 is not just a pediatric problem but may affect the patient for decades resulting in profound intellectual disability, severe motor handicap, and abnormal electroencephalography without active epilepsy. Other diagnostic hints in adults are small size, spasticity and severe abrasion due to amelogenesis imperfecta of the hypoplastic type.

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