“Liver Failure in an Infant of Late-Onset Glutaric Aciduria Type II”: Case Report

Abstract

Glutaric aciduria type II, also known as Multiple acyl-CoA Dehydrogenase Deficiency, results from a defect in the mitochondrial electron transport chain resulting in an inability to break down fatty-acids and amino acids. There are three phenotypes- type 1 and 2 are of neonatal onset and severe form, with and without congenital anomalies, respectively, and presents with acidosis, severe hypotonia, cardiomyopathy, hepatomegaly, and non-ketotic hypoglycemia. Type 3 or late-onset Multiple acyl-CoA Dehydrogenase Deficiency usually presents in the adolescent or adult age group with phenotype ranging from mild forms of myopathy and exercise intolerance to severe forms of acute metabolic decompensation on its chronic course. Type 3 Multiple acyl-CoA Dehydrogenase Deficiency rarely presents in infancy and in liver failure. We present a five-month-old developmentally normal female child with acute encephalopathy, hypotonia, non-ketotic hypoglycemia, metabolic acidosis, and liver failure, with a history of sibling death of suspected inborn error of metabolism. The blood acyl-carnitine levels in Tandem Mass Spectrometry and urinary organic acid analysis through Gas Chromatography–Mass Spectrometry were unremarkable. The patient initially responded to riboflavin, CoQ, and supportive management but ultimately succumbed to sepsis with shock and multi-organ dysfunction. The clinical exome sequencing reported a homozygous missense variation in exon 11 of the ETFDH gene (chr4:g.158706270C > T) that resulted in the amino acid substitution of Leucine for Proline at codon 456 (p.Pro456Leu) suggestive of Glutaric aciduria type IIc (OMIM#231,680).

Background

Glutaric aciduria type II, also known as Multiple Acyl-CoA Dehydrogenase Deficiency (MADD) or Electron Transfer Flavoprotein Deficiency (OMIM 231,680) is a rare autosomal recessive inborn error of metabolism affecting one in 200,000 live births [1–3]. There are about 350 published cases till date [4]. It can be caused by mutations in one of the three genes – Electron Transfer Flavoprotein Alpha subunit (ETFA, chr. 15q24.2–24.3), Electron Transfer Flavoprotein Beta subunit (ETFB, chr. 19q13.4–13.4) and Electron Transfer Flavoprotein Coenzyme Q Oxidoreductase (ETFDH, chr. 4q32-35) resulting in deficiency or absence of multiple acyl-CoA dehydrogenases [1–3]. This leads to a block in electron transfer to the respiratory chain resulting in an inability to break down fatty acids and branched-chain amino acids, lysine, and tryptophan leading to accumulation of these substrates and glutaric acid [1–3]. Glutaric aciduria type II has three phenotypes- the first two, which are of neonatal onset and severe form, with or without congenital anomalies, is mainly associated with mutations in the ETFA and ETFB gene, and presents with life-threatening symptoms of metabolic derangements, severe hypotonia, cardiomyopathy, hepatomegaly, non-ketotic hypoglycemia and is invariably fatal [1–3, 5]. The third phenotype, usually associated with ETFDH mutation, has a later age of onset, presenting in older children and adolescent-adult age group, has varied clinical presentation with about 80% presenting as isolated progressive myopathy and exercise intolerance with 20% presenting with acute episodes of metabolic decompensation (intermittent vomiting, metabolic acidosis, hypoglycemic encephalopathy and cardiac involvement) [1–4, 6]. There are very few case reports of late-onset MADD presenting in infancy [4, 7, 8], with liver failure being a very rare presentation [4, 5, 9]. We hereby present a case of glutaric aciduria type II with ETFDH mutation with infantile onset and severe phenotype with liver failure.

Case Report

A five-month old exclusively breast-fed, completely immunized, and nutritionally normal female child, second in birth order to a non-consanguineous couple, presented with loose stools, vomiting, lethargy, and seizures in the form of uprolling of eyes. The baby was born as term, by normal vaginal delivery, with a birth weight of 2.5 kg with uneventful perinatal history. The child had serially attained the developmental milestones in all domains till then. The patient at presentation, had poor efforts of breathing, Glasgow coma score of E2V2M4, hypotonia, and hypoglycemia (blood sugar of 26 mg/dL), requiring emergent management with mechanical ventilation and dextrose boluses to stabilize the patient. On secondary survey, the patient had axial and appendicular hypotonia, diminished power of less than 3/5 in all the limbs, diminished reflexes, cherry-red spots, massive hepatomegaly (span of 11 cm), but a normal head circumference. The parents had another male child who died at the age of one year with pneumonia and liver disease, and liver biopsy was suggestive of moderate mixed steatosis, which further strengthened the suspicion of an inborn error of metabolism in the present case. The blood sample was grossly lipemic, and the initial investigations were suggestive of high anion gap metabolic acidosis (pH- 7.15, pCO2- 22, bicarbonate- 8.5) with elevated lactate (4.91 mmol/L), elevated ammonia- 283 mcmol/L, absent urine ketones and reducing substances, deranged liver function tests (total bilirubin- 3.56 mg/dL with a direct bilirubin of 2.52 mg/dL, AST > 1000 U/L, ALT- 533 U/L, ALP- 266 IU/L, total proteins- 4.13 gm/dL), deranged coagulation profile (PT > 100 s., aPTT > 180 s), hyponatremia – 126 mmol/L, hypokalemia- 2.2 mmol/L, with baseline creatinine of 0.3 mg/dL, with evidence of sepsis. A differential diagnosis of fatty acid oxidation defects, glycogen storage disease type I, hyperinsulinism, and organic acidemia were kept. Supportive ventilatory management, antibiotics, vitamin K, fluids with a glucose infusion rate of 6-8 mg/kg/min, electrolyte and acid–base management, and a cocktail of vitamin supplements- biotin, thiamine, L-carnitine, CoQ10, vitamin C, riboflavin, vitamin B12, pyridoxine, and folinic acid were started and continued. Tandem Mass Spectrometry (TMS) on dried blood sample and Gas Chromatography-Mass Spectrometry (GCMS) on urine sample on continued feeds were negative. Serum insulin and C-peptide levels of the critical sample at the time of hypoglycemia were normal. However, alpha fetoproteins were elevated (Table 1). Due to a lack of etiological diagnosis, clinical exome sequencing was sent. The patient had initial partial response to the treatment in the form of improvement of encephalopathy and control of seizures, but by the fourth day, the patient deteriorated and developed consolidation of right upper and middle lobes of the lung, myocarditis as revealed by ECG changes of ST segment elevation and elevation of cardiac enzymes (Table 1), worsening of sepsis in the form of leucopenia (total leucocyte count- 3.95 × 10³/mL) and thrombocytopenia – 112 × 10³/mL, and acute kidney injury (creatinine- 2.2 mg/dL). There was worsening of the multiple organ functions despite the continuation of supportive management of acute kidney injury, shock, metabolic acidosis, encephalopathy, and sepsis. Peritoneal dialysis was also done in view of persistent anuria and encephalopathy. On the fourteenth day, the patient ultimately succumbed to severe sepsis with shock and multiple organ dysfunction. The clinical exome sequencing reported a homozygous missense variation in exon 11 of the ETFDH gene (chr4:g.158706270C > T) that resulted in the amino acid substitution of Leucine for Proline at codon 456 (p.Pro456Leu) suggestive of Glutaric aciduria type IIc (OMIM#231,680). The parents were counseled for their genetic analysis, but it could not be done due to financial constraints. Also, the need for genetic counseling for future pregnancies was explained.

Table 1.

Blood investigations

	Patient’s levels	Reference range
Troponin I (ng/mL)	0.123	0.02–0.06
Creatinine kinase (U/L)	> 2000	34–145
Insulin (mU/L)	23.15	3–25
C-peptide (ng/mL)	0.41	0.81–3.85
Cortisol (mcg/dL)	47.30	4.30–22.40
Alpha-feto protein (AFP) (ng/ml)	85.8	0–8
Free carnitine levels (mcmol/L)	5.63	> 7

Discussion

Under normal circumstances, fasting results in fatty acid oxidation and amino acid breakdown in the mitochondrion of the liver cells resulting in the formation of ketone bodies- acetoacetate and beta-hydroxybutyrate, which serves as an alternate fuel to the brain, heart, and skeletal muscles [5]. In glutaric aciduria type II (MADD), the block in the electron transfer chain results in impaired ketogenesis and lack of energy to the body’s vital organs, leading to multi-organ failure in our case [1–3, 5]. Early presentation in the neonatal age group (type 1 and type 2) usually presents with severe metabolic decompensation like hyperammonemia, non-ketotic hypoglycemia, severe metabolic acidosis, hypotonia, encephalopathy, and cardiomyopathy [2, 3, 6]. Type 3 or the late-onset form which presents beyond the neonatal period is the most common variant of glutaric aciduria type II (61.9%) [5], and is mainly caused by a mutation in the ETFDH gene (93.1%) [4], as in our case. A systemic review of 350 published cases of late-onset MADD reported the mean age of onset to be 19.2 years [4], with only a few cases presenting in infancy, as in our case [4, 7, 8]. Chronic manifestations of myopathy and exercise intolerance is the most common symptom, in as many as 85.3% of cases of late-onset MADD, of whom 20.4% have presented as acute decompensation on a chronic course precipitated by stress or infection [4]. Only a minority of late-onset MADD present acutely [4], as in our patient. Liver failure or acute Reye-like illness has mainly been reported in type 1, type 2, and adults of type 3 variety of MADD. Liver failure in children of late-onset MADD, like in our case, is a rare presentation [4, 5, 9]. Sweaty feet odor, which is characteristically present in the disease [2, 3], was absent in our case. The diagnosis is usually made by elevated blood acylcarnitine levels (C4-C18 species) and/or demonstration of an increased dicarboxylic acid, glutaric acid, 2-hydroxyglutarate, ethymalonic acid, glycine conjugates, etc. without ketonuria in urinary organic acid analysis [3, 4]. Our patient demonstrated a negative TMS and urinary GCMS despite being in a metabolically decompensated state, which may be seen in patients with severe carnitine depletion (free carnitine- 5.63 mcmol/L) [3, 4]. Elevated alpha fetoproteins may be explained on the basis of liver failure. The diagnosis of our patient was made through clinical exome sequencing, which is the gold standard test for establishing the diagnosis [1–4]. We report a homozygous missense variation in exon 11 of the ETFDH gene (chr4:g.158706270C > T) that resulted in the amino acid substitution of Leucine for Proline at codon 456 (p.Pro456Leu).

The ETFDH gene encodes for the Electron Transfer Flavoprotein Coenzyme Q Oxidoreductase, which forms an integral part of Complex II of the Mitochondrial Electron Transport Chain. During beta-oxidation of fatty acids, acyl-CoA dehydrogenase catalyzes the transfer of electrons from FAD (Flavin Adenine Dinucleotide) then to ETF (Electron Transferring Flavoprotein) and then to ETF:Q oxidoreductase (Electron Transfer Flavoprotein coenzyme Q oxidoreductase) (Fig. 1). This enzyme then passes the electron to the Ubiquinone and then to complex III [10]. The ETFDH gene is located on chromosome number 4 and consists of 617 amino acid residues [11]. The structure of the gene as obtained on X-ray crystallography reveals three, nearly connected functional regions: FAD-binding domain, 4Fe4S cluster and Ubiquinone binding domain [11]. An ADP-binding motif is localized in between the FAD-binding domain, and two membrane-binding surface antigens are identified in between the Ubiquinone binding domain [11]. The 456th codon in the EFTDH gene represents the Ubiquinone-binding domain that resulted in the amino acid substitution of Leucine for Proline (Fig. 1) [12].

Fig. 1.

a Electron Transport Chain b Complex II of Electron Transport Chain- During beta-oxidation of fatty acids, acyl-CoA dehydrogenase catalyzes the transfer of electrons from FAD (Flavin Adenine Dinucleotide) then to ETF (Electron Transferring Flavoprotein) and then to ETF:Q oxidoreductase (Electron Transfer Flavoprotein coenzyme Q oxidoreductase). This enzyme then passes the electron to the Ubiquinone and then to complex III. c The structure of the EFTDH gene as obtained on X-ray crystallography[11]: reveals three nearly connected functional regions namely, FAD-binding domain, 4Fe4S cluster, and Ubiquinone binding domain (amino acids 1–617). An ADP-binding motif is localized in between the FAD-binding domain, and two membrane-binding surface antigens are identified in between the Ubiquinone binding domain. The 456th codon in the EFTDH gene represents the Ubiquinone-binding domain that resulted in the amino acid substitution of Leucine for Proline

The proline residue is highly conserved, and there is a moderate physiochemical difference between proline and leucine [12]. Mutation in the Pro456Leu location of the ETFDH gene has been previously reported with milder variants and is usually riboflavin responsive [13–15], but our patient had a more severe form. It may be due to poor genotype–phenotype correlation in patients of late-onset MADD. The treatment comprises the restriction of fat and proteins, giving a high carbohydrate diet, riboflavin (100–400 mg/day) and CoQ supplementation [2, 3]. Flavin Adenine Dinucleotide (FAD) co-factor acts as an electron receiver in the Electron Transfer Flavoprotein (ETF). Riboflavin is a FAD precursor, making it a rational choice for therapy [9]. Our patient had an initial response to treatment, but finally succumbed to severe sepsis, metabolic decompensation, and multi-organ failure.

Conclusion

This case briefly highlights the various aspects of diagnosis and management of this rare disease. Also, it strengthens the existing literature. It will also help the parents in genetic counseling for future pregnancies.

Abbreviations

ETFA

Electron Transfer Flavoprotein Alpha subunit

ETFB

Electron Transfer Flavoprotein Beta subunit

ETFDH

Electron Transfer Flavoprotein Coenzyme Q Oxidoreductase

GCMS

Gas Chromatography-Mass Spectrometry

FAD

Flavin Adenine Dinucleotide

MADD

Multiple acyl-CoA Dehydrogenase Deficiency

TMS

Tandem Mass Spectrometry

Funding

Nil.

Declarations

Conflicts of interest

The authors declare that they have no conflict of interest,

Consent for Publication

Informed written consent was taken from parents for publication.