Inborn Errors of Ketogenesis: Novel Variants, Clinical Presentation, and Follow-Up in a Series of Four Patients.

Inborn errors of ketogenesis are rare disorders that result in acute and fulminant decompensation during lipolytic stress, particularly in infants and children. These include mitochondrial 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (HMGCS) deficiency and HMG-CoA lyase (HMGCL) deficiency. In this series, we describe the clinical, biochemical, and molecular profiles of four patients along with dietary interventions and their outcomes on a long-term follow-up. Two patients each of HMGCS and HMGCL deficiency were evaluated with clinical history, biochemical investigations, including tandem mass spectrometry (TMS) and urine gas chromatography-mass spectrometry (GCMS). Molecular analysis was performed by whole-exome sequencing, as well as exon array validated by long-range polymerase chain reaction. All individuals were diagnosed with acute metabolic decompensation in the early infancy period except one with HMGCL deficiency who had the first presentation at 5 years of age. Central nervous system manifestations, severe metabolic acidosis, hyperammonemia, hypoglycemia with a normal lactate, and absence of urinary ketones were observed in all the affected individuals. The disorder was life-threatening in three individuals and one succumbed to the illness. TMS was nonspecific and urine GCMS revealed dicarboxylic aciduria in HMGCS deficiency. Both the patients with HMGCL deficiency demonstrated elevated 3 hydroxyisovaleryl carnitine levels in TMS and metabolites of leucine degradation in urine GCMS. We identified five novel variants that included a large deletion involving exon 2 in HMGCL gene. There was no evidence of long-term neurological sequelae in the living individuals. Diet with moderation of fat intake was followed in two individuals with HMGCS deficiency. Low leucine and protein diet with moderation of fat intake was followed in the individual with HMGCL deficiency. All affected individuals are thriving well with no further major metabolic decompensation.

A Young Female With Medium-Chain Acyl-CoA Dehydrogenase Deficiency (MCADD): A Case Report.

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency (MCADD) is a rare autosomal recessive inborn error of mitochondrial fatty acid oxidation. MCAD is essential for fatty acid ß-oxidation during hepatic ketogenesis, which provides a major source of energy once hepatic glycogen stores are exhausted during extended fasting and periods of increased energy demand. The inability to metabolize these fatty acids results in hypoketotic hypoglycemia and the accumulation of toxic partially metabolized fatty acids. Intercurrent infection, extended fasting, excessive alcohol intake, vomiting, or diarrhea can lead to serious illness, including encephalopathy and even sudden death. Young people with MCADD are followed up on a regular basis by their metabolic disease specialist, and they are informed about risk factors as they advance through adolescence and adulthood. They should also carry along a written emergency management plan and relevant contact numbers. We describe a case of a 17-year-old female who attended her local emergency care center complaining of severe abdominal pain, vomiting, muscle ache, and poor oral intake. She was known to have MCADD; however, her emergency care plan had a date from eight years ago. She made a rapid recovery after receiving intravenous glucose and other therapies. The patient's concerns and knowledge about MCADD were not fully appreciated at the initial stage due to the rare nature of the disease. This in combination with the absence of current notes on the system, an emergency care plan dated from eight years ago, and the need to obtain specialist advice led to a slight delay in commencing specific therapy. This case report serves as a reminder of the emergency presentation of young people with MCADD, emphasizing the importance of effective communication between the patient, their parents, and the treating clinicians, obtaining the emergency care plan and recommendations, and communicating with the metabolic disease specialist.

MPV17 mutation-related mitochondrial DNA depletion syndrome: A case series in infants.

MPV17 is a mitochondrial inner membrane protein, involved in transporting deoxynucleotides into the mitochondria. Pathogenic MPV17 mutations can cause mitochondrial deoxyribonucleic acid (DNA) depletion syndrome, which has a varied presentation with neurological, muscular and hepatic involvement. Presentation as liver failure is relatively uncommon. Here, we report four infants from four separate families with pathogenic, homozygous MPV17 mutations. All had predominant hepatic involvement with cholestasis, lactic acidosis and hypoketotic hypoglycemia. Three of them had presented with liver failure. Interestingly, one of them showed fluctuating liver functions, which worsened with infection and improved after aggressive treatment with antibiotics and supplements. Two of the four cases died in infancy, while the other two improved on conservative management with medium-chain triglyceride-based diet, vitamin supplements, co-enzyme Q and carnitine. The two surviving children are alive at 12 and 25 months of age with native liver with normal to mildly deranged liver function and no neurological dysfunction. Next-generation sequencing confirmed the diagnosis in all of our cases. One of the detected mutations, c.55delC (p.Gln19ArgfsTer3) is a novel pathogenic frameshift mutation, while another mutation c.388G>C (p.Ala130Pro), which was previously reported in Single Nucleotide Polymorphism Database in heterozygous form, is being predicted as likely pathogenic in our case series. We, therefore, propose mutation testing for MPV17 gene during evaluation of indeterminate infantile liver failure, especially those with hypoglycemia and raised plasma lactate.

One case of mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase deficiency and literature review / 中国基层医药

Objective:To summarize the clinical phenotype and genetic characteristics of one child patient with mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase deficiency (mHS) caused by HMGCS2 gene mutation. Methods:One child patient with mHS who received treatment in Chongqing University Three Gorges Hospital on April 10, 2020 was included in this patient. The child was hospitalized due to cough, shortness of breath and deep coma. After admission, gas chromatography-mass spectrometry of the blood and urine samples and high-throughput whole genome sequencing were performed. The pedigree of the child with gene mutation was analyzed. The child was diagnosed with mHS. Related publications published by June, 2020 were searched in Wanfang database, Chinese Journal Full Text Database, PubMed and HGMD databases using search terms "mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase deficiency", "HMGCS2" "mHS deficiency". Forty-three papers addressing mHS deficiency were retrieved. The clinical phenotype and genotypes of the child with HMGCS2 mutation were summarized. Results:As of June 2020, there were 44 children with mHS deficiency, including the child reported in this study. These children consisted of 15 males, 11 females and 18 unknown genders. Among these children, 29 were aged 0-24 months, 4 were aged > 24 months, 6 had no symptoms, and 5 were of unknown age of disease onset. The first symptoms of most children were fever, cough, acute gastroenteritis, and coma. Twenty-seven children had hypoglycemia, 21 children had metabolic acidosis, 15 children developed hepatomegaly, 16 children had increased FFA/D-3-HB, and 10 children were tested 4-hydroxy-6-methyl-2-pyrone positive. The child included in this study had hepatomegaly, elevated alanine aminotransferase and metabolic acidosis. Gas chromatography-mass spectrometry results showed that a variety of metabolites were increased. Tandem mass spectrometry results showed that C40 level was elevated, and long-chain carnitine contents were increased. High-throughput whole genome sequencing results revealed that there were two heterozygous mutations in HMGCS2 gene, (NM_0055) c.559+1G > A; c. 758 T > C heterozygous mutation. Sanger sequencing and parental origin analysis showed that the mutations in this child were from parents. The two gene mutations in this child were new mutations, which have not been reported in China and countries outside China. According to the criteria and guidelines for interpretation of ACMG sequence variation, the variation was determined to be pathogenic. Conclusion:When a child has hypoketotic hypoglycemia and/or metabolic acidosis, increased FFA/D-3-HB and acetylcarnitine levels, mHS deficiency should be considered. HMGCS2 gene examination can help diagnose mHS deficiency.

Varón de 30 años con hiperamonemia de 24 horas de evolución / 30-year-old man with Acute Hyperammonemia

La hiperamonemia es una de las complicaciones agudas más graves que se puede presentar en diversos trastornos congénitos del metabolismo como los defectos en el ciclo de la urea, las acidemias orgánicas o en las alteraciones en la oxidación de los ácidos grasos. Su reconocimiento y tratamiento es una emergencia clínica, dado que el efecto neurotóxico es directamente proporcional al tiempo de exposición a niveles elevados de amonio. Presentamos el caso clínico de un paciente de 30 años con deterioro del nivel de consciencia y elevación del amonio plasmático de 24 horas de evolución. (AU)

Hyperammonemia is one of the most severe acute complication that can occur in various congenital metabolic conditions such as the urea cycle disorders, organic acidemias or fatty acids oxidation defects. The prompt recognition and treatment is a clinical emergency, since the neurotoxic effect is directly proportional to the time of exposure to high levels of ammonia. We report the clinical case of a 30-year-old patient with a decreased level of consciousness and a 24-hour evolution of high plasma ammonia. (AU)

Hereditary Tyrosinemia Compounded With Hyperinsulinemic Hypoglycemia: Challenging Diagnosis of a Rare Case.

Hereditary tyrosinemia type 1 (HT-1) is a rare autosomal recessive disorder caused by a deficiency in the enzyme fumarylacetoacetate hydrolase (FAH), which catalyzes the final step in the tyrosine degradation pathway. Hereditary tyrosinemia is a heterogeneous disease with a wide spectrum of clinical manifestations involving hepatic, renal, or nervous systems. It has grave consequences if left untreated. Some of the late complications of hereditary tyrosinemia include cirrhosis, liver nodules, hepatocellular carcinoma, hypophosphatemic rickets, nephrocalcinosis, glomerulosclerosis, and chronic renal failure. Rarely, infants with hereditary tyrosinemia may present with persistent hypoglycemia, which may be a result of acute liver failure or hyperinsulinism. Hyperinsulinemic hypoglycemia (HH), caused by dysregulation of insulin secretion from pancreatic ß-cells, leads to insulin driven glucose entry into the tissues and inhibits glycolysis, gluconeogenesis, fatty acid release, and ketone body synthesis. Hyperinsulinemic hypoglycemia can cause severe, persistent hypoketotic hypoglycemia. Diagnosing tyrosinemia type 1 can be a challenge as it is a heterogeneous disorder with a wide variety of clinical manifestations and complications. We herein report a rare case of a three-day-old male neonate with HT-1 compounded with HH.

Hypoketotic hypoglycemia in citrin deficiency: a case report.

BACKGROUND: Citrin deficiency (CD) is a recessive metabolic disease caused by biallelic pathogenic variants in SLC25A13. Although previous studies have reported ketosis in CD, it was observed at the time of euglycemia or mild hypoglycemia. Blood ketone levels concomitant with symptomatic or severe hypoglycemia in CD have not been a topic of focus despite its importance in identifying the etiology of hypoglycemia and assessing the ability of fatty acid utilization. Herein, we describe a patient with CD who had repeated episodes of hypoglycemia with insufficient ketosis. CASE PRESENTATION: A 1-year-old boy with repetitive hypoglycemia was referred to us to investigate its etiology. The fasting load for 13 h led to hypoketotic hypoglycemia, indicating the possibility of partial ß-oxidation dysfunction. A genetic test led to the diagnosis of CD. The hypoglycemic episodes disappeared after switching to a medium-chain triglyceride-containing formula. CONCLUSIONS: This case report suggests that symptomatic or severe hypoglycemia in patients with CD could be associated with relatively low levels of ketone bodies, implying that ß-oxidation in these patients might possibly be partially disrupted. When encountering a patient with hypoglycemia, clinicians should check blood ketone levels and bear in mind the possibility of CD because excessive intravenous administration of glucose can cause decompensated symptoms in patients with CD as opposed to other disorders presenting with hypoketotic hypoglycemia, such as fatty acid oxidation disorders. Further studies in a large-scale cohort are warranted to confirm our speculation.

Novel HMGCS2 pathogenic variants in a Chinese family with mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase deficiency.

IMPORTANCE: Mitochondrial 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase deficiency is a rare and underdiagnosed disorder with fewer than 30 patients reported worldwide. The application of whole-exome sequencing in patients could improve our understanding of this disorder. OBJECTIVE: To identify the genetic causes and evaluate the phenotype of mitochondrial HMG-CoA synthase deficiency in a pediatric patient with uncommon features that included ketosis and elevated lactate and ammonia. METHODS: The proband was referred to the pediatric intensive care unit of Beijing Children's Hospital and selected for molecular testing with whole-exome sequencing. Her parents and sibling also underwent sequencing for segregation information. RESULTS: We identified two novel mutations (c.1347_1351delAGCCT/p.Ala450Profs*7 and c.1201G>T/ p.Glu401*) in the HMG-CoA synthase-2 gene (HMGCS2, NM_005518.3) in the proband and her brother. Both variants were classified as pathogenic variants according to the American College of Medical Genetics and Genomics/ Association for Molecular Pathology guidelines. Metabolic acidosis in the proband was corrected with continuous renal replacement therapy and she left hospital after 21 days of treatment. INTERPRETATION: Our results extend the genotypic and phenotypic spectrum of HMGCS2 mutation in mitochondrial HMG-CoA synthase deficiency patients and serve as a reminder for physicians to consider mitochondrial HMG-CoA synthase deficiency in newborns and children with coma and hypoketotic hypoglycemia after fasting.

Fatty acid oxidation disorders.

Fatty acid oxidation disorders (FAODs) are inborn errors of metabolism due to disruption of either mitochondrial ß-oxidation or the fatty acid transport using the carnitine transport pathway. The presentation of a FAOD will depend upon the specific disorder, but common elements may be seen, and ultimately require a similar treatment. Initial presentations of the FAODs in the neonatal period with severe symptoms include cardiomyopathy, while during infancy and childhood liver dysfunction and hypoketotic hypoglycemia are common. Episodic rhabdomyolysis is frequently the initial presentation during or after adolescence; although, these symptoms may develop at any age for most of the FAODs The treatment of all FAOD's include avoidance of fasting, aggressive treatment during illness, and supplementation of carnitine, if necessary. The long-chain FAODs differ by requiring a fat-restricted diet and supplementation of medium chain triglyceride oil and often docosahexaenoic acid (DHA)-an essential fatty acid, crucial for brain, visual, and immune functions and prevention of fat soluble vitamin deficiencies. The FAOD are a group of autosomal recessive disorders associated with significant morbidity and mortality, but early diagnosis on newborn screening (NBS) and early initiation of treatment are improving outcomes. There is a need for clinical studies including randomized, controlled, therapeutic trials to continue to evaluate current understanding and to implement future therapies.

Defectos de la oxidación de ácidos grasos como causa de hipoglucemia no cetósica en el niño / Fat acid oxidation defects produce nonketotic hypoglycemia in childhood

Fatty acid oxidation defects (FAOD) cause a group of inherited metabolic diseases that impair mitochondrial energy production from lipids. The clinical presentation includes hypoketotic hypoglycaemia, acute liver failure, myocardiopathy and myopathy after a prolonged fasting. Inheritance is autosomal recessive and the global incidence is 1:10.000 newborn, varying between 1:9.000 and 1:60.000 newborns for medium-chain acyl-CoA dehydrogenase deficiency (MCAD), the most frequent FAOD. Therapy is dietary and pharmacological. As soon as the diagnosis is confirmed enough glucose to prevent lipolysis must be introduced, especially in the neonatal period and during metabolic derangements caused by infections. Nutritional treatment consists in avoiding any period of fasting by giving carbohydrate supplement when appetite is diminished, which is easy and inexpensive to do. The prognosis with presymptomatic diagnosis is excellent when done with a blood sample obtained in the neonatal period and analysed by tandem mass spectrometry, and when treatment is started immediately.

Los defectos de oxidación de los ácidos grasos corresponden a un grupo de alteraciones metabólicas hereditarias que afectan la producción intramitocondrial de energía a partir de los lípidos. Clínicamente se expresan con hipoglucemia no cetósica, insuficiencia hepática aguda, miocardiopatía o miopatía desencadenada por un ayuno prolongado. La herencia es autosómica recesiva y su frecuencia global se estima en 1:10.000 recién nacidos (RN), y entre 1 por 9 000 a 1 por 60 000 RN para el déficit de acil-CoA deshidrogenasa de cadena media (abreviado MCAD) defecto más frecuente en este grupo de patologías. Las medidas terapéuticas pueden ser dietéticas y farmacológicas. Una vez establecido el diagnóstico diferencial del tipo de defecto, es importante proporcionar suficiente cantidad de glucosa para prevenir la lipólisis del tejido adiposo, siendo fundamental en el período neonatal y las en descompensaciones metabólicas por infecciones. El tratamiento es fácil de aplicar y de bajo costo y consiste en fraccionar la alimentación para evitar el ayuno prolongado. El pronóstico es excelente cuando el diagnóstico es presintomático, a través del análisis de una muestra de sangre en papel filtro, para el estudio de acilcarnitinas por espectrometría en tandem durante el período de RN e iniciando el fraccionamiento de la dieta inmediatamente.

Fatty acid oxidation disorders / 한양의대학술지

Inborn errors of fatty acid mitochondrial oxidation (FAOD) have drawn considerable attention in recent years because of rapid pace of discovery of new defects and an ever-increasing spectrum of clinical phenotypes. This review describes a clinical and biochemical phenotypes, diagnosis and treatment of FAOD. Some of FAOD can not be detected by conventional biochemical investigations, even when a patient is symptomatic with fasting intolerance or functional failure of fatty acid dependent tissue (s). Diagnosis must ultimately be based on direct assay of the involved enzyme, however, preliminary indicators may come from determination of carnitine and intermediate metabolites in plasma, profiling of urine organic acid, and radioisotopic screening assays with lymphocytes or cultured fibroblasts. We are faced with the following major challenges: whether to include FAOD in newborn screening programs, the investigation of the rules played by individual disorders in maternal complication during pregnancy, sudden and unexpected death in early life, and pediatric acute/fulminant liver failure.