A novel electron transfer flavoprotein dehydrogenase (ETFDH) gene mutation identified in a newborn with glutaric acidemia type II: a case report of a Chinese family

Background

Glutaric acidemia type II (GA II) or multiple acyl-CoA dehydrogenase deficiency (MADD, OMIM 231680) is an inherited autosomal recessive disease affecting fatty acid, amino acid and choline metabolism, due to mutations in one of three genes namely, electron transfer flavoprotein alpha-subunit, ETFA, electron transfer flavoprotein β-subunit, ETFB and electron transfer flavoprotein dehydrogenase, ETFDH. Currently, few studies have reported genetic profiling of neonatal-onset GA II. This study aimed to identify the genetic mutations in a Chinese family with GA II.

Case presentation

We reported a case of GA II with purulent meningitis and septicemia and identified a novel ETFDH gene mutation in a female infant. The patient developed an episode of hypoglycemia and hypotonicity on the postnatal first day. Laboratory investigations revealed elevations of multiple acylcarnitines indicating glutaric acidemia type II in newborn screening analysis. Urinary organic acids were evaluated for the confirmation and revealed a high glutaric acid excretion. Genetic analysis revealed two mutations in the ETFDH gene (c.623_626 del / c. 1399G > C), which were considered to be the etiology for the disease. The novel mutation c.623_626 del was identified in the proband infant and her father, her mother was carriers of the mutation c.1399G > C.

Conclusions

A novel variant (c.623_626 del) and a previously reported missense (c.1399G > C) in the ETFDH gene have been identified in the family. The two variants of ETFDH gene identified probably underlie the pathogenesis of Glutaric acidemia type II in this family, and also enlarge ETFDH genotype-phenotype correlations spectrum.

Flavin adenine dinucleotide synthase deficiency due to FLAD1 mutation presenting as multiple acyl-CoA dehydrogenation deficiency-like disease: A case report

Multiple acyl-CoA dehydrogenase deficiency (MADD), also known as glutaric acidemia type II, is classically caused by a congenital defect in electron transfer flavoprotein (ETF) or ETF dehydrogenase (ETFDH). Flavin adenine dinucleotide synthase (FADS) deficiency caused by mutations in FLAD1 was recently reported as a novel riboflavin metabolism disorder resembling MADD. Here, we describe a Japanese boy with FADS deficiency due to a novel mutation (p.R249*) in FLAD1. In the asymptomatic male infant born at full term, newborn screening showed positive results with elevated C5 and C14:1 acylcarnitine levels and an increased C14:1/C2 ratio. Biochemical studies were unremarkable except for lactic acidosis (pH 7.197, lactate 61 mg/dL). A diagnosis of MADD was suspected because of mild abnormalities of the acylcarnitine profile and apparent abnormalities of urinary organic acids, although mutations in the ETFA, ETFB, ETFDH, and riboflavin transporter genes (SLC52A1, SLC52A2, and SLC52A3) were not detected. Administration of riboflavin and L-carnitine was initiated at one month of age based on the diagnosis of "biochemical MADD" despite a lack of symptoms. Nevertheless, the acylcarnitine profile was not normalized. Symptoms resembling bulbar palsy, such as vocal cord paralysis and dyspnea with stridor, were present from 3 months of age. At 4 months of age, he became bedridden because of hypoxic-ischemic encephalopathy due to fulminant respiratory failure with aspiration pneumonia. At 2 years and 5 months of age, a homozygous c.745C > T (p.R249*) mutation in the FLAD1 gene was identified, confirming the diagnosis of FADS deficiency. His severe clinical course may be caused by this nonsense mutation associated with poor responsiveness to riboflavin. Persistent lactic acidosis and neuropathy, such as bulbar palsy, may be important for diagnosing FADS deficiency. Although the biochemical findings in FADS deficiency are similar to those in MADD, their clinical symptoms and severity may not be identical.

Glutaric acidemia type II patient with thalassemia minor and novel electron transfer flavoprotein-A gene mutations: A case report and review of literature

Glutaric acidemia type II (GAII), also known as multiple acyl-CoA dehydrogenase deficiency, is an autosomal recessive inborn error of amino acid and fatty acid metabolism. We report a case of GAII with novel electron transfer flavoprotein (ETF)-A mutations in a 2-year-old female with thalassemia minor. The patient developed an episode of hypoglycemia and hypotonicity on the postnatal first day. Laboratory investigations revealed elevations of multiple acyl carnitines indicating glutaric acidemia type II in newborn screening analysis. Urinary organic acids were evaluated for the confirmation and revealed a high glutaric acid excretion. Genetic analysis revealed two novel mutations in the ETF-A gene, which are considered to be compound heterozygote. At the 8 mo of life ketone therapy was added, which significantly increased the neuromotor development. The patient had been closely followed for two years with carnitine, riboflavin, coenzyme Q10, and ketone supplementation in addition to a high carbohydrate diet. Although the patient had comorbidity like thalassemia minor, her neuromotor development was normal for her age and had no major health problems. This specific case expands the previously reported spectrum of this disease.

Efficacy of bezafibrate on fibroblasts of glutaric acidemia type II patients evaluated using an in vitro probe acylcarnitine assay

INTRODUCTION

We evaluated the effects of bezafibrate (BEZ) on β-oxidation in fibroblasts obtained from patients with glutaric acidemia type II (GA2) of various clinical severities using an in vitro probe (IVP) assay.

METHODS

Cultured fibroblasts from 12 patients with GA2, including cases of the neonatal-onset type both with and without congenital anomalies (the prenatal- and neonatal-onset forms, respectively), the infantile-onset, and the myopathic forms, were studied. The IVP assay was performed by measuring acylcarnitines (ACs) in the cell culture medium of fibroblasts incubated with palmitic acid for 96h in the presence of 0-800μM BEZ using tandem mass spectrometry.

RESULTS

The IVP assay showed that 100μM BEZ markedly reduced the level of palmitoylcarnitine (C16) in the neonatal-onset, infantile-onset, and myopathic forms of GA2, either increasing or maintaining a high level of acetylcarnitine (C2), which serves as an index of energy production via β-oxidation. In the prenatal-onset form, although a small reduction of C16 was also observed in the presence of 100μM BEZ, the level of C2 remained low. At concentrations higher than 100μM, BEZ further decreased the level of ACs including C16, but a concentration over 400μM decreased the level of C2 in most cases.

DISCUSSION

BEZ at 100μM was effective for all GA2 phenotypes except for the prenatal-onset form, as a reduction of C16 without deterioration of C2 is considered to indicate improvement of β-oxidation. The effects of higher doses BEZ could not be estimated by the IVP assay but might be small or nonexistent.