Characterization of two ETFDH mutations in a novel case of riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency

Sara Missaglia,Corrado Angelini,Laura Moro,Daniela Tavian

doi:10.1186/s12944-018-0903-5

Abstract

BackgroundDeficiency of electron transfer flavoprotein dehydrogenase (ETFDH) is associated with multiple acyl-CoA dehydrogenase deficiency (MADD). This disorder is an autosomal recessive lipid storage myopathy (LSM) that exhibits a wide range of clinical features, including myopathy, weakness and multisystem dysfunctions. Many patients with late onset of MADD improve when treated with riboflavin and are also referred to as RR-MADD (riboflavin-responsive multiple Acyl-CoA dehydrogenase disorder).MethodsIn this study, we report the clinical and genetic characterization of a novel RR-MADD patient. Biochemical data were obtained from analysis of muscle and plasma samples. DNA and RNA were extracted from peripheral blood, and sequence analysis and expression study of ETFDH gene were performed. Finally, the impact of mutations on ETFDH folding was evaluated using bioinformatic tools.ResultsPatient initially presented with vomiting, muscle weakness, and acidosis. Muscle biopsy revealed typical myopathological patterns of lipid storage myopathy and blood acylcarnitine profiles showed a combined elevation of long and medium chain acylcarnitines, supporting the diagnosis of RR-MADD. Molecular analysis of ETFDH gene revealed two heterozygous mutations, a novel splice variation in intron 10, c.1285 + 1G > A, and the previously reported c.560C > T missense mutation. RT-PCR analysis showed an alteration of ETFDH RNA splicing which in turn should lead to the production of a truncated protein. The in silico prediction analysis of ETFDH tridimensional structure demonstrated that the missense mutation resulted in instability and loss of protein activation, while the splice site variation induced a dramatic conformational change of the truncated protein. After MCT diet supplemented with carnitine and riboflavin, the patient showed significant biochemical and clinical improvement, in spite of severe molecular defect.ConclusionThis case report extends the spectrum of ETFDH mutations in MADD, providing further evidence that patients presenting at least one missense mutation in the FAD-binding domain may respond to either carnitine or riboflavin treatment, due to the recovery of some enzymatic activity.

Highlights

Deficiency of electron transfer flavoprotein dehydrogenase (ETFDH) is associated with multiple acylCoA dehydrogenase deficiency (MADD)
Electron transfer flavoprotein dehydrogenase (ETFDH), called ETF-ubiquinone oxidoreductase, is a mitochondrial protein localized in the inner membrane, that plays a key role in the electron-transfer system [1]
Serum and urinary determinations of carnitine were below normal (3.74 micromol/dL and 11.408 micromol/24 h, respectively). She was discharged with a diagnose of carnitine deficiency myopathy and supplemented with DL-carnitine therapy for 6 g/day and Medium chain triglycerides (MCT) diet and physical therapy recommended

Summary

Introduction

Deficiency of electron transfer flavoprotein dehydrogenase (ETFDH) is associated with multiple acylCoA dehydrogenase deficiency (MADD) This disorder is an autosomal recessive lipid storage myopathy (LSM) that exhibits a wide range of clinical features, including myopathy, weakness and multisystem dysfunctions. Tachypnea, hepatomegaly, metabolic acidosis and hypoketotic hypoglycemia arise within the first 24– 48 h of life and the death often occurs within the first weeks of life; 3) mild and/or late onset (MADD type III). In this case, the patients show a variable age of disease onset and different clinical symptoms: lipid storage myopathy, cardiac damage, intermittent episodes of vomiting and metabolic acidosis. The treatment can include a low-fat diet with carnitine and MCT supplementation [8, 9, 11]

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