Acute fatty liver of pregnancy associated with short-chain acyl-coenzyme A dehydrogenase deficiency

Characterization of pregnancy outcome of women with an offspring with inborn errors of metabolism: A population-based study

Introduction: Inborn errors of metabolism (IEM) are scarce, and their diagnosis is often made after birth. This has led to the perception that most fetuses affected by these disorders do not become clinically apparent during pregnancy. Our aim was to determine the obstetrical characteristics of women with an offspring affected by IEM.

Methods: This population-based retrospective cohort study included all women who delivered at the Soroka University Medical Center (SUMC) from 1988 to 2017 who met the inclusion criteria. Mothers who had an offspring with IEM were included in the study group, and those who had offsprings without IEM comprised the comparison group.

Results: A total of 388,813 pregnancies were included in the study, and 184 of them were complicated by a fetus with IEM. The number of Bedouin women was higher in the IEM-affected infant group than in the comparison group (90.8% vs. 53.3%, p < 0.001); women who had a fetus with IEM had a higher rate of polyhydramnios (7.1% vs. 3.2%, p = 0.005), HELLP syndrome (3.3% vs. 1.1%, p = 0.014), and preterm birth (20.7% vs. 10.1%, p < 0.001); neonates with IEM had lower mean birth weight (p < 0.001), lower Apgar scores at 1′ and 5′ minutes (p < 0.001), and a higher rate of fetal growth restriction (FGR) (p < 0.001), postpartum death <28 days (p < 0.001), and neonatal death (p < 0.001) than those in the comparison group. Pregnancies with IEM fetuses were independently associated with preterm birth (OR 2.00; CI 1.4–3), polyhydramnios (OR 2.08; CI 1.17–3.71), and FGR (OR 2.24; CI 1.2–4.19). Each family of metabolic diseases is independently associated with specific pregnancy complications (i.e., mitochondrial diseases are associated with HELLP syndrome (OR 5.6; CI 1.8–17), and lysosomal storage disease are associated with nonimmune hydrops fetalis (OR 26.4; CI 3.39–206).

Conclusion: This study reports for the first time, an independent association of IEM with specific complications of pregnancy. This observation has clinical implications, as the identification of specific pregnancy complications in a population at risk for IEM can assist in the prenatal diagnosis of an affected fetus.

Analysis of clinical characteristics and genetic testing in patients with acute fatty liver of pregnancy: a retrospective study

Background

Acute fatty liver of pregnancy (AFLP) is an acute, rare and potentially lethal disease typically occurring in the third trimester of pregnancy. So far, there is no effective means of prevention. Therefore, in this study, we retrospectively analyzed the clinical features of AFLP patients for a better understanding. Meanwhile, for the first time, the genetic background associated with the onset of AFLP was discussed by high-throughput sequencing, hoping to provide evidence for genetic counseling and prenatal diagnosis of AFLP.

Methods

Thirteen AFLP patients admitted to our hospital and other hospital from March 2012 to February 2020 were selected. Clinical data about general condition, laboratory test, liver biopsy and the prognosis of mother and fetus were collected for retrospective analysis. In addition, the peripheral blood of five patients with AFLP and one newborn infant of his mother with AFLP was sequenced with whole-exome sequencing and gene mutation was analyzed by bioinformatics methods.

Results

The initial symptoms of AFLP varied differently, with jaundice (9/13, 69%), fatigue (8/13, 62%) and nausea and vomiting (6/13, 46%) being the most common. Moreover, the main maternal complications were coagulopathy (13/13, 100%), followed by acute renal dysfunction (10/13, 77%). Raised serum bilirubin, transaminases and uric acid were found in all patients (100%), hypoglycemia was found in six patients (46%) and fatty liver on ultrasound was seen in five patients (5/12, 42%). One (7%) maternal death occurred and all neonates survived delivery. In addition, to our surprise, whole-exome sequencing showed that no gene mutation in related enzymes involved in fatty acid metabolism was noted in the pregnant women and children receiving genetic testing.

Conclusions

Early visit, early detection, early termination of pregnancy and multidisciplinary comprehensive treatment are the key factors to improve the prognosis of AFLP patients and their newborn infants. Furthermore, although limited size of study, to our knowledge, this report is the first to present the lack of common mutation involved in fatty acid oxidation in Chinese patients with AFLP via whole-exome sequencing. Thus, further studies are needed with larger and more varied samples to validate the conclusion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04095-8.

Comparison of maternal and neonatal outcomes between acute fatty liver of pregnancy and hemolysis, elevated liver enzymes and low platelets syndrome: a retrospective cohort study

BACKGROUND

Acute fatty liver of pregnancy (AFLP) and hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome are two uncommon disorders that mimic each other clinically, but are distinct pathophysiologically. This study aimed to compare maternal and neonatal outcomes between AFLP and HELLP syndrome.

METHODS

This retrospective cohort study was performed at a tertiary referral center in Taiwan between June 2004 and April 2020. We used the Swansea Criteria to diagnose AFLP, and the Tennessee Classification System to diagnose HELLP syndrome. Maternal characteristics, laboratory data, complications, and neonatal outcomes were compared. We analyzed the categorical variables with Chi-square test or Fisher's exact test and continuous variables with Student's t test or Mann-Whitney U test. Subsequent logistic regression analyses adjusting by potential confounding factors with significant difference were analyzed.

RESULTS

During the study period, 21 women had AFLP and 80 women had HELLP syndrome. There was a higher rate of preeclampsia (95.0 % versus 23.8 %) in the HELLP syndrome group compared to the AFLP group. However, the AFLP group had more other maternal complications including jaundice (85.7 % versus 13.8 %), acute kidney injury (61.9 % versus 15.0 %), disseminated intravascular coagulopathy (66.7 % versus 8.8 %), and sepsis (47.6 % versus 10.0 %) compared to the HELLP syndrome group. Nevertheless, higher rates of small for gestational age neonates (57.1 % versus 33.3 %), neonatal respiratory distress syndrome (39.2 % versus 8.3 %) and neonatal sepsis (34.2 % versus 12.5 %) were noted in the HELLP syndrome group.

CONCLUSIONS

AFLP is associated with a higher rate of multiple organ dysfunction in mothers, whereas HELLP syndrome is associated with a higher rate of neonatal morbidity.

Lipid Myopathies

Disorders of lipid metabolism affect several tissues, including skeletal and cardiac muscle tissues. Lipid myopathies (LM) are rare multi-systemic diseases, which most often are due to genetic defects. Clinically, LM can have acute or chronic clinical presentation. Disease onset can occur in all ages, from early stages of life to late-adult onset, showing with a wide spectrum of clinical symptoms. Muscular involvement can be fluctuant or stable and can manifest as fatigue, exercise intolerance and muscular weakness. Muscular atrophy is rarely present. Acute muscular exacerbations, resulting in rhabdomyolysis crisis are triggered by several factors. Several classifications of lipid myopathies have been proposed, based on clinical involvement, biochemical defect or histopathological findings. Herein, we propose a full revision of all the main clinical entities of lipid metabolism disorders with a muscle involvement, also including some those disorders of fatty acid oxidation (FAO) with muscular symptoms not included among previous lipid myopathies classifications.

Embryonic lethality in mice due to carnitine transporter OCTN2 defect and placental carnitine deficiency

l-Carnitine plays a crucial role in uptake and subsequent β-oxidation of long-chain fatty acids in the mitochondria. Placental trophoblast cells oxidize long-chain fatty acids for energy production. Here we present data showing that l-carnitine deficiency due to a defect in the carnitine transporter OCTN2 (SLC22A5) in a mouse model leads to embryonic lethality. Placental levels of l-carnitine are reduced to <10% of normal and deficiency of l-carnitine is associated with markedly reduced expression of several growth factors and transforming growth factor β (TGF-β) genes. This report links for the first time reduced l-carnitine levels in the placenta to embryonic lethality.

Short-chain acyl-CoA dehydrogenase deficiency: from gene to cell pathology and possible disease mechanisms

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is an inherited disorder of mitochondrial fatty acid oxidation that is characterized by the presence of increased butyrylcarnitine and ethylmalonic acid (EMA) concentrations in plasma and urine. Individuals with symptomatic SCADD may show relatively severe phenotype, while the majority of those who are diagnosed through newborn screening by tandem mass spectrometry may remain asymptomatic. As such, the associated clinical symptoms are very diverse, ranging from severe metabolic or neuromuscular disabilities to asymptomatic. Molecular analysis of affected individuals has identified rare gene variants along with two common gene variants, c.511C > T and c.625G > A. In vitro studies have demonstrated that the common variants as well as the great majority of rare variants, which are missense variants, impair folding, that may lead to toxic accumulation of the encoded protein, and/or metabolites, and initiate excessive production of ROS and chronic oxidative stress. It has been suggested that this cell toxicity in combination with yet unknown factors can trigger disease development. This association and the full implications of SCADD are not commonly appreciated. Accordingly, there is a worldwide discussion of the relationship of clinical manifestation to SCADD, and whether SCAD gene variants are disease associated at all. Therefore, SCADD is not part of the newborn screening programs in most countries, and consequently many patients with SCAD gene variants do not get a diagnosis and the possibilities to be followed up during development.

[Acute fatty liver of pregnancy and mitochondrial fatty acid oxidation. Consequences for the offspring]

Acute fatty liver of pregnancy (AFLP) is a rare liver disease unique to pregnancy that can lead to acute liver failure. The prognosis, initially often fatal for both mother and child, has been improved by prompt delivery. The diagnosis should be highly suspected if the mother presents epigastric pain, nausea and/or vomiting, or polyuria-polydipsia in the third trimester of pregnancy. AFLP has been found associated with a genetic deficiency of fatty acid beta-oxidation, which may cause sudden death in infancy. Consequently, the mother and her newborn should undergo screening for this deficiency.

Acute Fatty Liver Disease of Pregnancy: Updates in Pathogenesis, Diagnosis, and Management

Acute fatty liver of pregnancy (AFLP) is an obstetric emergency characterized by maternal liver failure and may have complications for the mother and fetus, including death. This review examines recent literature on the epidemiology, pathogenesis, diagnosis, and treatment of acute fatty liver of pregnancy. Pathogenesis of this disease has been linked to defects in fatty acid metabolism during pregnancy, especially in the setting of fetal genetic defects in fatty acid oxidation. The value of screening all patients for these genetic defects remains to be determined. Distinguishing AFLP from other high-risk liver diseases of pregnancy that have overlap features, such as HELLP and preeclampsia, can be challenging. Although sensitive diagnostic tools such as the Swansea criteria have been developed, further work is needed to diagnose AFLP more quickly. Although survival rates have improved in the past 30 years, delay in diagnosis and treatment of AFLP has life-threatening consequences; an algorithmic approach to AFLP may be a valuable resource for clinicians. Future epidemiological and long-term studies will improve our prediction of women at risk for developing AFLP and determine the long-term consequences of this condition.

Immunology of hepatic diseases during pregnancy

The mother's immune system has to adapt to pregnancy accepting the semi-allograft fetus and preventing harmful effects to the developing child. Aberrations in feto-maternal immune adaptation may result in disease of the mother, such as liver injury. Five pregnancy-associated liver disorders have been described so far, however, little is known concerning immune alterations promoting the respective disease. These liver disorders are pre-eclampsia, hemolysis, elevated liver enzymes, low platelet count (HELLP), acute fatty liver, hyperemesis gravidarum, and intrahepatic cholestasis of pregnancy. On the other hand, pre-existing autoimmune liver injury of the mother can be affected by pregnancy. This review intends to summarize current knowledge linking feto-maternal immunology and liver inflammation with a special emphasis on novel potential biomarkers.

Caring for the woman with acute fatty liver of pregnancy

Acute fatty liver of pregnancy, although rare, is usually a third trimester of pregnancy occurrence that may be life threatening for both the pregnant woman and the fetus. Often, the onset resembles gastroenteritis or cholecystitis and correct diagnosis is delayed. Because it can also present with preeclampsia and eclampsia, it may be mistakenly diagnosed as hemolysis, elevated liver enzymes, low platelet syndrome. This article presents diagnostic differences between liver conditions that can complicate pregnancy and management strategies for treating and maintaining the well-being of pregnant women, fetuses, and infants who are affected by acute fatty liver of pregnancy. Early recognition and rapid intervention from antepartum diagnosis through delivery and the postpartum period are required by the nursing team and medical providers to reduce maternal and neonatal morbidity and mortality.

[Acute fatty liver in pregnancy: revealing fetal fatty acid oxidation disorders]

Acute fatty liver of pregnancy (AFLP) and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome are serious maternal illnesses occurring in the third trimester of pregnancy with significant perinatal and maternal mortality. AFLP may result from mitochondrial defects in the beta-oxidation of fatty acids, in particular a deficiency of the long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) in the fetus. Clinical findings in AFLP vary and its diagnosis is complicated by a significant overlap in clinical and biochemical features with HELLP syndrome. We report the case of 2 siblings who died, the first one in the neonatal period of asphyxia with multivisceral presentation and the second one from sudden death at 7 months. Autopsy of the latter infant revealed hepatic steatosis associated with cardiomyopathy, which led to suspicion of a fatty acid oxidation deficiency. Mutation analysis demonstrated that both children were homozygous for the common mutation c.1528G>C and the parents were heterozygous for this same mutation. This case demonstrates the importance of screening mothers with acute fatty liver disease of pregnancy and their children at birth for a metabolic disease. This article proposes several metabolic tests for mother and child suspected of having beta-oxidation of a fatty acid disorder.

A Rare Case of Short-Chain Acyl-COA Dehydrogenase Deficiency: The Apparent Rarity of the Disorder Results in Under Diagnosis

Short-chain acyl-CoA dehydrogenase (ACAD) deficiency is an extremely rare inherited mitochondrial disorder of fat metabolism. This belongs to a group of diseases known as fatty acid oxidation disorders. Screening programmes have provided evidence that all the fatty acid oxidation disorders combined are among the most common inborn errors of metabolism. Mitochondrial beta oxidation of fatty acids is an essential energy producing pathway. It is a particularly important pathway during prolonged periods of starvation and during periods of reduced caloric intake due to gastrointestinal illness or increased energy expenditure during febrile illness. The most common presentation is an acute episode of life threatening coma and hypoglycemia induced by a period of fasting due to defective hepatic ketogenesis. Here, the case of a 4 month old female patient who had seizures since the third day of her birth and persistent hypoglycemia is described. She was born to parents of second degree consanguinity after 10 years of infertility treatment. There was history of delayed cry after birth. Metabolic screening for TSH, galactosemia, 17-OHP, G6PD, cystic fibrosis, biotinidase were normal. Tandem mass spectrometric (TMS) screening for blood amino acids, organic acids, fatty acids showed elevated butyryl carnitine (C4) as 3.40 μmol/L (normal <2.00 μmol/L), hexanoyl carnitine (C6) as 0.92 μmol/L (normal <0.72 μmol/L), C4/C3 as 2.93 μmol/L (normal <1.18 μmol/L). The child was started immediately on carnitor syrup (carnitine) 1/2 ml twice daily. Limitation of fasting stress and dietary fat was advised. Baby responded well by gaining weight and seizures were controlled. Until now, less than 25 patients have been reported worldwide. The limited number of patients diagnosed until now is due to the rarity of the disorder resulting in under diagnosis.

Liver diseases unique to pregnancy: a 2010 update

Liver disorders occurring during pregnancy may be specifically pregnancy-related, or may be due to an intercurrent or chronic liver disease, which may present in anyone, pregnant or not. This review focuses on the liver diseases unique to pregnancy. Hyperemesis gravidarum, which occurs during early pregnancy, may be associated with liver dysfunction. Intrahepatic cholestasis of pregnancy typically occurs during the second or third trimester. Pruritus and the associated biological signs of cholestasis improve rapidly after delivery. Mutations in gene encoding biliary transporters, especially ABCB4 encoding the multidrug resistance 3 protein, have been found to be associated with this complex disease. Ursodeoxycholic acid is currently the most effective medical treatment in improving pruritus and liver tests. Pre-eclampsia, which presents in late pregnancy frequently involves the liver, and HELLP syndrome (Hemolysis-Elevated Liver enzymes-Low Platelets) is a life-threatening complication. Prognosis of acute fatty liver of pregnancy has been radically transformed by early delivery, and clinicians must have a high index of suspicion for this condition when a woman presents nausea or vomiting, epigastric pain, jaundice, or polyuria-polydipsia during the third trimester. Acute fatty liver of pregnancy has been found to be associated with a defect of long-chain 3-hydroxyacyl coenzyme A dehydrogenase in the fetus, and mothers and their offspring should undergo DNA testing at least for the main associated genetic mutation (c.1528G>C).

Clinical aspects of short-chain acyl-CoA dehydrogenase deficiency

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is an autosomal recessive inborn error of mitochondrial fatty acid oxidation. SCADD is biochemically characterized by increased C4-carnitine in plasma and ethylmalonic acid in urine. The diagnosis of SCADD is confirmed by DNA analysis showing SCAD gene mutations and/or variants. SCAD gene variants are present in homozygous form in approximately 6% of the general population and considered to confer susceptibility to development of clinical disease. Clinically, SCADD generally appears to present early in life and to be most frequently associated with developmental delay, hypotonia, epilepsy, behavioral disorders, and hypoglycemia. However, these symptoms often ameliorate and even disappear spontaneously during follow-up and were found to be unrelated to the SCAD genotype. In addition, in some cases, symptoms initially attributed to SCADD could later be explained by other causes. Finally, SCADD relatives of SCADD patients as well as almost all SCADD individuals diagnosed by neonatal screening remained asymptomatic during follow-up. This potential lack of clinical consequences of SCADD has several implications. First, the diagnosis of SCADD should never preclude extension of the diagnostic workup for other potential causes of the observed symptoms. Second, patients and parents should be clearly informed about the potential lack of relevance of the disorder to avoid unfounded anxiety. Furthermore, to date, SCADD is not an optimal candidate for inclusion in newborn screening programs. More studies are needed to fully establish the relevance of SCADD and solve the question as to whether SCADD is involved in a multifactorial disease or represents a nondisease.

A case of severe preeclampsia leading to the diagnosis of de novo abnormal fatty acid metabolism and ACE gene deletion

BACKGROUND

Enzymes involved in the metabolism of free fatty acids are essential for the proper use of caloric intake. Abnormal enzymes unable to degrade fatty acids will result in an accumulation of fatty acids in organs like the liver, impairing its function.

CASE

A 28-year-old primigravid woman underwent induction of labour because of severe preeclampsia. She was subsequently found to be a carrier for mutations in several fatty acid enzymes as well as the angiotensin converting enzyme.

CONCLUSION

During pregnancy, the increased need for fatty acid degradation will expose women who are carriers of mutations in these enzymes. The clinical manifestations in such women include acute fatty liver of pregnancy that may mimic severe preeclampsia. Strict metabolic control to avoid excess fatty acid degradation may allow for better pregnancy outcomes and newborn assessment.

Short-chain acyl-coenzyme A dehydrogenase deficiency

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is a disorder of mitochondrial fatty acid oxidation that leads to the accumulation of butyrylcarnitine and ethylmalonic acid in blood and urine. Originally described with a relatively severe phenotype, most patients are now diagnosed through newborn screening by tandem mass spectrometry and remain asymptomatic. Molecular analysis of affected individuals has identified a preponderance of private inactivating point mutations and one common one present in high frequency in individuals of Ashkenazi Jewish ancestry. In addition, two polymorphic variants have been identified that have little affect on enzyme kinetics but impair folding and stability. Individuals homozygous for one of these variants or compound heterozygous for one of each often show an increased level of ethylmalonic acid excretion that appears not to be clinically significant. The combination of asymptomatic affected newborns and the frequent variants can cause much confusion in evaluating and treating individuals with SCADD. The long-term consequences and the need for chronic therapy remain current topics of contention and investigation.

Short-chain acyl-CoA dehydrogenase (SCAD) deficiency: an examination of the medical and neurodevelopmental characteristics of 14 cases identified through newborn screening or clinical symptoms

The medical and neurodevelopmental characteristics of 14 children with short-chain acyl-CoA dehydrogenase deficiency (SCADD) are described. Eight were detected as neonates by newborn screening. Three children diagnosed on the basis of clinical symptoms had normal newborn screening results while three were born in states that did not screen for SCADD. Treatment included frequent feedings and a low fat diet. All children identified by newborn screening demonstrated medical and neuropsychological development within the normative range on follow-up, although one child had a relative weakness in the motor area and another child exhibited mild speech delay. Of the three clinically identified children with newborn screening results below the cut-off value, two were healthy and performed within the normal range on cognitive and motor tests at follow-up. Four clinically identified children with SCADD experienced persistent symptoms and/or developmental delay. However, in each of these cases, there were supplementary or alternative explanations for medical and neuropsychological deficits. Results indicated no genotype-phenotype correlations. These findings suggest that SCADD might be benign and the clinical symptoms ascribed to SCADD reflective of ascertainment bias or that early identification and treatment prevented complications that may have occurred due to interaction between genetic susceptibility and other genetic factors or environmental stressors.

The ACADS gene variation spectrum in 114 patients with short-chain acyl-CoA dehydrogenase (SCAD) deficiency is dominated by missense variations leading to protein misfolding at the cellular level

Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is an inherited disorder of mitochondrial fatty acid oxidation associated with variations in the ACADS gene and variable clinical symptoms. In addition to rare ACADS inactivating variations, two common variations, c.511C > T (p.Arg171Trp) and c.625G > A (p.Gly209Ser), have been identified in patients, but these are also present in up to 14% of normal populations leading to questions of their clinical relevance. The common variant alleles encode proteins with nearly normal enzymatic activity at physiological conditions in vitro. SCAD enzyme function, however, is impaired at increased temperature and the tendency to misfold increases under conditions of cellular stress. The present study examines misfolding of variant SCAD proteins identified in patients with SCAD deficiency. Analysis of the ACADS gene in 114 patients revealed 29 variations, 26 missense, one start codon, and two stop codon variations. In vitro import studies of variant SCAD proteins in isolated mitochondria from SCAD deficient (SCAD-/-) mice demonstrated an increased tendency of the abnormal proteins to misfold and aggregate compared to the wild-type, a phenomenon that often leads to gain-of-function cellular phenotypes. However, no correlation was found between the clinical phenotype and the degree of SCAD dysfunction. We propose that SCAD deficiency should be considered as a disorder of protein folding that can lead to clinical disease in combination with other genetic and environmental factors.

[Recurrent acute fatty liver of pregnancy]

Acute fatty liver of pregnancy (AFLP) is a rare liver disease unique to pregnancy potentially fatal for both mother and child. Only a few cases of recurrence have been published. We report a new case. A 27-year-old primiparous patient presented a first episode of AFLP in 1991 at 37 week's gestation. Diagnosis was suspected because of vomiting, thrombocytopenia, and liver function tests abnormalities. It was confirmed by liver ultrasonography and abdominal computed tomography. Clinical and biological improvement was observed after caesarean delivery. Six years later, the woman began a second pregnancy. Liver function tests and complete blood count were regularly checked. At 30 weeks' gestation, recurrent AFLP occurred and caesarean section was performed. Again, diagnosis was confirmed by both ultrasonography and abdominal computed tomography. In 2006, the mother and the two girls, 15 and 8-year-old respectively, were in good health. The study of the HADHA gene, coding alpha subunit long chain 3-hydroxyacyl coenzyme A dehydrogenase (LCHAD) in the patient failed to find mutations, particularly the common mutation c.1528G>C (Glu474-Gln, p.E474Q). In conclusion, after an episode of AFLP, women should be clearly warned of the risk of recurrence and regularly monitored during the next pregnancy, even if the search of HADHA gene mutation is negative.

Short-chain acyl-CoA dehydrogenase gene mutation (c.319C>T) presents with clinical heterogeneity and is candidate founder mutation in individuals of Ashkenazi Jewish origin

We report 10 children (7 male, 3 female), 3 homozygous for c.319C>T mutation and 7 heterozygous for c.319C>T on one allele and c.625G>A variant on the other in the short-chain acyl-CoA dehydrogenase (SCAD) gene (ACADS). All were of Ashkenazi Jewish origin in which group we found a c.319C>T heterozygote frequency of 1:15 suggesting the presence of a founder mutation or selective advantage. Phenotype was variable with onset from birth to early childhood. Features included hypotonia (8/10), developmental delay (8/10), myopathy (4/10) with multicore changes in two and lipid storage in one, facial weakness (3/10), lethargy (5/10), feeding difficulties (4/10) and congenital abnormalities (3/7). One female with multiminicore myopathy had progressive external ophthalmoplegia, ptosis and cardiomyopathy with pneumonia and respiratory failure. Two brothers presented with psychosis, pyramidal signs, and multifocal white matter abnormalities on MRI brain suggesting additional genetic factors. Two other infants also had white matter changes. Elevated butyrylcarnitine (4/8), ethylmalonic aciduria (9/9), methylsuccinic aciduria (6/7), decreased butyrate oxidation in lymphoblasts (2/4) and decreased SCAD activity in fibroblasts or muscle (3/3) were shown. Expression studies of c.319C>T in mouse liver mitochondria showed it to be inactivating. c.625G>A is a common variant in ACADS that may confer disease susceptibility. Five healthy parents were heterozygous for c.319C>T and c.625G>A, suggesting reduced penetrance or broad clinical spectrum. We conclude that the c.319C>T mutation can lead to wide clinical and biochemical phenotypic variability, suggesting a complex multifactorial/polygenic condition. This should be screened for in individuals with multicore myopathy, particularly among the Ashkenazim.

Highly active antiretroviral therapy does not affect mitochondrial beta-oxidation of fatty acids: an in vitro study in fibroblasts

Preeclampsia is a multifactorial pregnancy-specific disease. In some cases, severe preeclampsia and related disorders of acute fatty liver of pregnancy and hemolysis, elevated liver enzymes, low platelets syndrome are associated with inherited defects in mitochondrial beta-oxidation of fatty acids, especially a deficiency of long-chain 3-hydroxyacyl coenzyme A dehydrogenase (LCHAD). Recently, an unexplained increase in the incidence of preeclampsia has been documented in human immunodeficiency virus (HIV)-infected pregnant women on treatment with highly active antiretroviral therapy (HAART). We performed this study to determine if antiretroviral drugs affect mitochondrial beta-oxidation fatty acids in vitro. Two normal and 1 heterozygous LCHAD-deficient cell lines were exposed to up to 5 times the therapeutic concentrations of the following antiretroviral drugs: nevirapine, didanosine, lamivudine, and a combination of nelfinavir, zidovudine, and lamivudine. One homozygous LCHAD-deficient cell line served as the positive control. After exposure of the fibroblasts to these drugs for periods ranging from 2 to 10 days, accumulations of even-chain 3-hydroxy fatty acids (3-OH-C6 to 3-OH-C18) in the culture media were measured by stable-isotope dilution gas chromatography/mass spectrometry. Compared to the respective unexposed fibroblasts, there was no significant build-up of 3-hydroxy fatty acids in the culture media of normal or heterozygous LCHAD-deficient fibroblasts exposed to antiretroviral drugs. Our results show that the commonly used antiretroviral drugs do not adversely affect fatty acid oxidation in fibroblasts. Therefore, an altered fatty acid oxidation may not be the mechanism for the reported increased risk of preeclampsia in HIV-infected pregnant women on HAART.

No mutation was found in the alpha-subunit of the mitochondrial tri-functional protein in one patient with severe acute fatty liver of pregnancy and her relatives

BACKGROUND AND AIM

Acute fatty liver of pregnancy (AFLP) is a serious hepatic disorder and a devastating late gestational complication associated with substantial maternal and neonatal morbidity and mortality. Several studies have demonstrated a strong association between AFLP in the mother and fetal deficiency of the enzyme long-chain L-3 hydroxyacyl-CoA dehydrogenase (LCHAD). LCHAD resides in the alpha-subunit of the mitochondrial tri-functional protein and catalyzes the third step in the beta-oxidation of fatty acids in the mitochondria. The aim of this study was to determine in one patient with severe AFLP who survived liver transplantation, if the infant or her parents would bear the common or rare mutation of the LCHAD gene.

METHODS

Genomic DNA was extracted from the patient with severe AFLP and her daughter and parents. Exon 15 of LCHAD was amplified by polymerase chain reaction (PCR) and analyzed by restricted fragment length polymorphism (RFLP) with Pst-I. The whole coding region of LCHAD cDNA of all subjects was amplified and sequenced for the potential rare mutation.

RESULTS

None of the subjects had the G1528C mutation in the LCHAD gene. None of the subjects had mutation in the whole coding region of LCHAD or rare polymorphisms.

CONCLUSIONS

Although this study was limited to one proband and her relatives, our observations suggest that there might be diverse etiological factors in China contributing to AFLP other than the frequently reported mutation in the LCHAD, and the metabolic basis for AFLP may be more heterogeneous than previously believed.

Acute fatty liver of pregnancy: An update on pathogenesis and clinical implications

Acute fatty liver of pregnancy (AFLP) is a serious maternal illness occurring in the third trimester of pregnancy with significant perinatal and maternal mortality. Till recently, it has been considered a mysterious illness. In this editorial, we review the recent advances in understanding the pathogenesis of AFLP and discuss the studies documenting a fetal-maternal interaction with a causative association between carrying a fetus with a defect in mitochondrial fatty acid oxidation and development of AFLP. Further, we discuss the impact of these recent advances on the offspring born to women who develop AFLP, such that screening for a genetic defect can be life saving to the newborn and would allow genetic counseling in subsequent pregnancies. The molecular basis and underlying mechanism for this unique fetal-maternal interaction causing maternal liver disease is discussed.

Oxidative stress in experimental liver microvesicular steatosis: role of mitochondria and peroxisomes

BACKGROUND

Hepatic microvesicular steatosis is a clinical manifestation seen in a number of liver diseases. Although the role of mitochondrial beta-oxidation in the development of the disease has been well studied, information on lipid peroxidative damage in liver subcellular organelles is scarce. The present study looked at oxidative stress in hepatic peroxisomes and microsomes in microvesicular steatosis, using an animal model of the disease.

METHODS

Rats were given i.p. injections of sodium valproate (700 mg/kg bodyweight) to induce microvesicular steatosis, which was confirmed by histology.

RESULTS

Oxidative stress was evident in liver in steatosis, accompanied by structural and functional alterations in hepatic mitochondria. Alterations in lipid composition, with decreased phosphatidyl choline and ethanolamine and increased lysophosphatidyl choline and ethanolamine, were seen. An increase in triglyceride content was also seen. In addition, increased lipid peroxidation was also evident in peroxisomes and microsomes from steatotic rats. Pretreatment with clofibrate results in partial reversal of changes produced by valproate.

CONCLUSIONS

These results suggest that in addition to impaired mitochondrial beta-oxidation, oxidative stress is also seen in the hepatic peroxisomes and microsomes during microvesicular steatosis.

Fetal fatty acid oxidation defects and maternal liver disease in pregnancy

OBJECTIVE

The objective was to evaluate the relationships between all types of fetal fatty acid oxidation defects and maternal liver disease, including acute fatty liver of pregnancy and hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome.

METHODS

This was a case-control study comparing fetal fatty acid oxidation defects to the outcome of maternal liver disease. Fifty case infants with fatty acid oxidation defects were identified, with 25 matched controls collected per case. This generated a total of 50 case infants and 1,250 control infants. Pregnancies were evaluated for the presence of maternal liver disease (comprised of acute fatty liver of pregnancy, HELLP syndrome, and preeclampsia evolving into HELLP syndrome) using a conditional logistic regression model. Subgroup analysis compared long chain to short and medium chain fatty acid defects.

RESULTS

Maternal liver disease was noted in 16.00% of all fatty acid oxidation defect pregnancies compared with 0.88% in the general population (odds ratio 20.4, 95% confidence interval 7.82-53.2). These pregnancies demonstrated an 18.1-fold increase in maternal liver disease when compared with our matched population controls with unaffected fetuses. All classifications of fatty acid oxidation defects were at high risk of developing maternal liver disease. Long chain defects were 50 times more likely than controls to develop maternal liver disease and short and medium chain defects were 12 times more likely to develop maternal liver disease.

CONCLUSION

Maternal liver disease is significantly higher across the entire spectrum of fatty acid oxidation defects pregnancies compared with the matched control population. Notably, there is significant risk to the pregnancies with fetuses affected with short and medium chain defects, not just those with fetal long chain fatty acid oxidation defects as previously reported. Future studies should examine the pathophysiology of all infant fatty acid oxidation defects and its implications for maternal liver disease for improved future health outcomes.

LEVEL OF EVIDENCE

II-2.

Perioperative management of a child with short-chain acyl-CoA dehydrogenase deficiency

Short-chain acyl-CoA dehydrogenase (SCAD) is a mitochondrial enzyme that catalyzes the dehydrogenation of short chain fatty acids (4 to 6 carbons in length) thereby initiating the cycle of beta-oxidation. This process generates acetyl-CoA, the key substrate for hepatic ketogenesis or ATP production by the Kreb's cycle. A deficiency of SCAD results in the build-up of potentially cytotoxic metabolites including ethylmalonic acid, methylsuccinyl CoA and butyryl-carnitine. The end-organ involvement is heterogeneous, but most commonly includes hypotonia with possible lipid myopathy and developmental delay. Other reported complications include dysmorphic craniofacial features, hypoglycemia, seizures, scoliosis, hypertonia and hyperreflexia, cyclic vomiting and myocardial dysfunction. We present a 23-month-old girl with SCAD deficiency, who required posterior fossa decompression for type 1 Chiari malformation. The potential perioperative implications of SCAD deficiency are reviewed.

Homogeneous amplification nucleobase quenching assay to detect the E474Q LCHAD deficiency mutation

Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency is a rare and potentially fatal autosomal recessive disorder of fatty acid metabolism. Early institution of dietary therapy is essential and places a premium on rapid diagnosis. Pregnancy with an LCHAD-deficient fetus is often complicated in the third trimester by liver disease, particularly acute fatty liver of pregnancy. All cases of isolated LCHAD deficiency have at least one copy of the E474Q mutation in the gene encoding the alpha-subunit of the mitochondrial trifunctional protein. Previously published methods for detecting this mutation are based upon allele-specific restriction enzyme digestion of a DNA fragment generated by PCR, followed by gel electrophoresis to resolve the products. We have developed a faster and less expensive assay for the E474Q mutation using PCR followed directly by differential melting of a fluorescently labeled oligodeoxyribonucleotide probe, using nucleobase quenching to detect probe hybridization.

Fetal fatty acid oxidation disorders, their effect on maternal health and neonatal outcome: impact of expanded newborn screening on their diagnosis and management

Mitochondrial fatty acid oxidation disorders (FAOD) are recessively inherited errors of metabolism. Newborns with FAOD typically present with hypoketotic hypoglycemia, metabolic acidosis, hepatic failure, and cardiomyopathy. Late presentations include episodic myopathy, neuropathy, retinopathy, and arrhythmias. Sudden unexpected death can occur at any age and can be confused with sudden infant death syndrome. Some FAOD are associated with intrauterine growth restriction, prematurity, and pregnancy complications in the heterozygous mother, such as severe preeclampsia, acute fatty liver of pregnancy (AFLP), or hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome. Maternal pregnancy complications occur primarily in mothers carrying a fetus with long-chain l-3-hydroxyacyl CoA dehydrogenase deficiency or general trifunctional protein deficiencies. FAOD as a group represent the most common inborn errors of metabolism, and presymptomatic diagnosis of FAOD is the key to reduce morbidity and avoid mortality. The application of tandem mass spectrometry to newborn screening provides an effective means to identify most FAOD patients presymptomatically. At the beginning of 2005, 36 state newborn screening programs have mandated or adopted this technology resulting in a marked increase in the number of asymptomatic neonates with FAOD diagnosed. To ensure the long-term benefits of such screening programs, pediatricians and other health care providers must be educated about these disorders and their treatment.

Lack of correlation between fatty acid oxidation disorders and haemolysis, elevated liver enzymes, low platelets (HELLP) syndrome?

AIM

Fatty acid beta-oxidation defects comprise a heterogeneous group of disorders that may precipitate acute life threatening metabolic crises particularly during catabolic episodes. Several studies have demonstrated a possible association between fatty acid beta-oxidation defects, including long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency and severe pregnancy complications. However, the precise percentage of women with haemolysis, elevated liver enzymes, low platelets (HELLP) syndrome associated with foetal fatty acid beta-oxidation defects is not known.

METHODS

We carried out a multicentre retrospective study on 88 infants, born to women with HELLP syndrome. Acylcarnitine profiles from blood dried on filter paper cards were analysed by tandem mass spectrometry for the diagnosis of fatty acid beta-oxidation defects. In addition, we screened for the common long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency mutation using a standard restriction fragment length polymorphism polymerase chain reaction method.

RESULTS

None of the infants studied carried the common long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency mutation. There was no evidence of fatty acid beta-oxidation defects, including long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency, as expected by unremarkable acylcarnitine profiles, while three infants with fatty acid beta-oxidation defects were diagnosed in the control group.

CONCLUSIONS

Neither foetal long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency, including heterozygosity for the common long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency mutation, nor fatty acid beta-oxidation defects in general are a major risk factor for HELLP syndrome in Austria.

Genetic defects in fatty acid beta-oxidation and acyl-CoA dehydrogenases. Molecular pathogenesis and genotype-phenotype relationships

Mitochondrial fatty acid oxidation deficiencies are due to genetic defects in enzymes of fatty acid beta-oxidation and transport proteins. Genetic defects have been identified in most of the genes where nearly all types of sequence variations (mutation types) have been associated with disease. In this paper, we will discuss the effects of the various types of sequence variations encountered and review current knowledge regarding the genotype-phenotype relationship, especially in patients with acyl-CoA dehydrogenase deficiencies where sufficient material exists for a meaningful discussion. Because mis-sense sequence variations are prevalent in these diseases, we will discuss the implications of these types of sequence variations on the processing and folding of mis-sense variant proteins. As the prevalent mis-sense variant K304E MCAD protein has been studied intensively, the investigations on biogenesis, stability and kinetic properties for this variant enzyme will be discussed in detail and used as a paradigm for the study of other mis-sense variant proteins. We conclude that the total effect of mis-sense sequence variations may comprise an invariable--sequence variation specific--effect on the catalytic parameters and a conditional effect, which is dependent on cellular, physiological and genetic factors other than the sequence variation itself.

A comparison of in vitro acylcarnitine profiling methods for the diagnosis of classical and variant short chain acyl-CoA dehydrogenase deficiency

BACKGROUND

Homozygosity and compound heterozygosity for the short chain acyl-CoA dehydrogenase (SCAD) gene sequence variants 625G-->A and 511C-->T are associated with ethylmalonic aciduria (EMA), a biochemical indicator of SCAD deficiency. The clinical and biochemical implications of these variants are not fully understood. The effect of these variants on the accumulation of butyrylcarnitine by fibroblasts in culture was studied.

METHODS

In vitro acylcarnitine profiling in fibroblasts was carried out using [U-13C]-labeled or unlabeled palmitate in the presence of excess L-carnitine, with or without a medium chain acyl-CoA dehydrogenase (MCAD) inhibitor. Acylcarnitines were analyzed using tandem mass spectrometry. 625G/625G (wild type), 625G/625A and 625A/625A (variant) control fibroblasts were compared with fibroblasts from patients homozygous for inactivating SCAD mutations (SCAD deficient) and from patients with EMA who were homozygous or compound heterozygous for the SCAD variants.

RESULTS

Variant control and patient fibroblasts accumulated moderate amounts of butyrylcarnitine compared with wild-type controls and in contrast to the significant amount of butyrylcarnitine accumulated by SCAD deficient fibroblasts, regardless of incubation conditions.

CONCLUSIONS

Moderately reduced SCAD activity associated with SCAD variants can be detected using in vitro acylcarnitine profiling methods, which may be used as an indirect measure of SCAD activity.

Short-chain Acyl-CoA dehydrogenase deficiency: studies in a large family adding to the complexity of the disorder

OBJECTIVE

To understand the expanding clinical and biochemical spectrum of short-chain acyl-CoA dehydrogenase (SCAD) deficiency, the impact of which is not fully understood.

STUDY DESIGN

We studied a family with SCAD deficiency and determined urinary ethylmalonic acid excretion, plasma C(4)-carnitine, SCAD enzyme activity in fibroblasts and lymphocytes, DNA mutations in the SCAD gene, and clinical expression. The index patient was born prematurely and had otherwise unexplained cholestasis and hepatomegaly during the first year of life. His mother developed a hemolysis-elevated liver enzymes-low platelets (HELLP) syndrome while pregnant with the index patient.

RESULTS

Two siblings had a homozygous inactivating 1138C>T mutation, whereas the father was compound heterozygous for this mutation and the common 625G>A polymorphism. There was a good correlation between the type of SCAD mutation, the residual SCAD enzyme activity, and the levels of urinary ethylmalonic acid and plasma C(4)-carnitine in each of the eight family members. Retrospective acylcarnitine analysis of the index patient's Guthrie screening card confirmed the abnormal increase of C(4)-carnitine, suggestive of SCAD deficiency. None of the family members had hypotonia, developmental delay, or episodes of ketotic hypoglycemia.

CONCLUSION

Homozygosity for an inactivating SCAD mutation does not necessarily result in disease. The previously held opinion that SCAD deficiency is always a serious disorder may have been influenced by a clinical bias. Homozygosity for an inactivating 1138C>T SCAD mutation was assessed by neonatal screening of blood spot acylcarnitines. SCAD deficiency may be associated with maternal HELLP syndrome.

Misfolding, degradation, and aggregation of variant proteins. The molecular pathogenesis of short chain acyl-CoA dehydrogenase (SCAD) deficiency

Short chain acyl-CoA dehydrogenase (SCAD) deficiency is an inborn error of the mitochondrial fatty acid metabolism caused by rare variations as well as common susceptibility variations in the SCAD gene. Earlier studies have shown that a common variant SCAD protein (R147W) was impaired in folding, and preliminary experiments suggested that the variant protein displayed prolonged association with chaperonins and delayed formation of active enzyme. Accordingly, the molecular pathogenesis of SCAD deficiency may rely on intramitochondrial protein quality control mechanisms, including degradation and aggregation of variant SCAD proteins. In this study we investigated the processing of a set of disease-causing variant SCAD proteins (R22W, G68C, W153R, R359C, and Q341H) and two common variant proteins (R147W and G185S) that lead to reduced SCAD activity. All SCAD proteins, including the wild type, associate with mitochondrial hsp60 chaperonins; however, the variant SCAD proteins remained associated with hsp60 for prolonged periods of time. Biogenesis experiments at two temperatures revealed that some of the variant proteins (R22W, G68C, W153R, and R359C) caused severe misfolding, whereas others (R147W, G185S, and Q341H) exhibited a less severe temperature-sensitive folding defect. Based on the magnitude of in vitro defects, these SCAD proteins are characterized as folding-defective variants and mild folding variants, respectively. Pulse-chase experiments demonstrated that the variant SCAD proteins either triggered proteolytic degradation by mitochondrial proteases or, especially at elevated temperature, aggregation of non-native conformers. The latter finding may indicate that accumulation of aggregated SCAD proteins may play a role in the pathogenesis of SCAD deficiency.

Rare disorders of metabolism with elevated butyryl- and isobutyryl-carnitine detected by tandem mass spectrometry newborn screening

Tandem mass spectrometry was adopted for newborn screening by North Carolina in April 1999. Since then, three infants with short-chain acyl-CoA dehydrogenase (SCAD) and one with isobutyryl-CoA dehydrogenase deficiency were detected on the basis of elevated butyrylcarnitine/isobutyrylcarnitine (C4-carnitine) concentrations in newborn blood spots analyzed by tandem mass spectrometry. For three SCAD-deficient infants, biochemical evaluation included a plasma acylcarnitine profile with markedly elevated C4-carnitine, urine organic acid analysis with markedly elevated ethylmalonic and 2-methylsuccinic acids, and markedly elevated [U-13C]butyrylcarnitine concentrations in medium from fibroblasts incubated with [U-13C]palmitic acid and excess l-carnitine, consistent with classic SCAD deficiency. Two of three infants diagnosed with classic SCAD deficiency remained asymptomatic; however, the third infant presented with seizures and a cerebral infarct at 10 wk of age. All three infants had putatively inactivating mutations in both alleles of the SCAD gene. The highly elevated plasma C4-carnitine levels in the three infants detected by newborn screening tandem mass spectrometry differentiated them from infants and children who were homozygous or compound heterozygous for one of two SCAD gene susceptibility variations; for the latter group the C4-carnitine levels were normal. Isobutyryl-CoA dehydrogenase deficiency in a fourth infant was confirmed after isolated elevation of C4-carnitine in the acylcarnitine profile.

Pregnancy and liver disease

Liver disease has an impact on women's health during pregnancy because of the complex interactions between the physiologic changes induced by pregnancy and the pathophysiologic changes of liver disease. In particular, liver diseases that predominantly afflict females, such as primary biliary cirrhosis and autoimmune hepatitis, pose a special problem for conception and management of pregnancy. Pregnancy, moreover, specifically is associated with several potentially life-threatening liver diseases. This article reviews comprehensively the impact of liver diseases on pregnancy and of pregnancy on liver function and liver disease.

Abdominal pain during pregnancy

Numerous medical, surgical, psychiatric, gynecologic, and obstetric disorders can cause abdominal pain during pregnancy. The patient history, physical examination, laboratory data, and radiologic findings usually provide the diagnosis. The pregnant woman has physiologic alterations that affect the clinical presentation, including atypical normative laboratory values. Abdominal ultrasound is generally the recommended radiologic imaging modality; roentgenograms are generally contraindicated during pregnancy because of radiation teratogenicity. Concerns about the fetus limit the pharmacotherapy. Maternal and fetal survival have recently increased in many life-threatening conditions, such as ectopic pregnancy, appendicitis, and eclampsia, because of improved diagnostic technology, better maternal and fetal monitoring, improved laparoscopic technology, and earlier therapy.

Diagnosis and management of defects of mitochondrial beta-oxidation

PURPOSE OF REVIEW

At least 22 different inborn errors of metabolism affecting beta-oxidation in skeletal muscle and other tissues have been identified in the past 30 years. Early diagnosis and therapeutic diets offer the best chance for normal growth and development in most patients.

RECENT FINDINGS

Clinical heterogeneity has become the hallmark of defects in beta-oxidation. In many cases a correct diagnosis will only be made if these disorders are specifically considered and appropriate studies are obtained, since screening tests which detect other inborn errors of metabolism are often normal in patients with beta-oxidation defects. Dietary management provides the only opportunity for therapy in many cases, including carbohydrate supplements intended to provide more extended delivery of glucose to the bloodstream. Use of a novel odd chain fat supplement as an alternative fuel source in long chain fat metabolism defects offers promise of alleviating muscular symptoms not well controlled by diet. The introduction of expanded newborn screening will lead to the recognition of an increasing number of individuals with these disorders, placing greater demand for services on practitioners knowledgeable in their therapy. Study of the clinical outcome in these patients will provide a better understanding of defects of beta-oxidation.

SUMMARY

Clinical symptoms, diagnostic testing, and issues of newborn screening for this important group of disorders are discussed.

Fetal genotypes and pregnancy outcomes in 35 families with mitochondrial trifunctional protein mutations

OBJECTIVE

The purpose of this study was to evaluate the effects of fetal genotype on maternal and fetal outcomes in families with mitochondrial trifunctional protein mutations in the United States. Trifunctional protein has 3 enzymatic activities that include long-chain 3-hydroxyacyl-CoA dehydrogenase, which catalyzes long-chain fatty acid beta-oxidation.

STUDY DESIGN

We analyzed pregnancy history and offspring genotypes in 35 families with heterogeneous mutations. The fetal genotype was determined in utero in 11 pregnancies and after birth in 50 pregnancies.

RESULTS

Forty-nine percent of the women who carried affected fetuses had acute fatty liver of pregnancy. Another 11% of the women had the syndrome of hemolysis, elevated liver enzymes, and low platelets, or preeclampsia. All women who had the maternal illness carried fetuses with isolated long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency. Sixty-eight percent and 43% of the affected pregnancies also were associated with premature delivery and intrauterine growth retardation, respectively. No maternal or fetal complications were associated with heterozygous or wild-type fetal genotypes.

CONCLUSION

Fetal mitochondrial trifunctional protein defects should be considered a cause for maternal liver disease, preterm labor, and intrauterine growth retardation.

Strategies for the diagnosis of mitochondrial fatty acid beta-oxidation disorders

Mitochondrial fatty acid beta-oxidation disorders (FAOD) are a group of clinically and biochemically heterogeneous inherited metabolic defects. The spectrum of phenotypes has expanded from hepatic encephalopathy to encompass myopathy, cardiomyopathy, peripheral neuropathy, sudden death and pregnancy complicated by fetal FAOD. Pre-symptomatic diagnosis is important to prevent morbidity and this is now achievable through newborn screening using tandem mass spectrometry (MS/MS). Moreover, most of the diagnosed defects are treatable and the prognosis is generally favourable. This article reviews the features of FAOD, critically evaluates methods of investigation including metabolite analyses in body fluids, in vitro oxidation rates and acylcarnitine profiling studies, enzymatic and mutational tests, and discusses genotype-phenotype correlation, treatment and monitoring options. Based on this knowledge, strategies for the biochemical investigation and differential diagnosis of patients presenting clinically, asymptomatic neonates detected by newborn screening, infants born after complications during late pregnancy, and cases of sudden death with suspected FAOD are presented. Laboratory investigation commonly begins with a search for diagnostic metabolites in physiological fluids, followed by in vitro functional studies if the initial findings are inconclusive, and confirmation by enzymology and molecular analyses. Occasionally a stress test in vivo may be required. At other times there may be no firm diagnosis achieved.

Long-chain L-3-hydroxyacyl-coenzyme a dehydrogenase deficiency: a molecular and biochemical review

Since the first report of long-chain L-3-hydroxyacyl-coenzyme A dehydrogenase deficiency a little more than a decade ago, its phenotypic and genotypic heterogeneity in individuals homozygous for the enzyme defect has become more and more evident. Even more interesting is its association with pregnancy-specific disorders, including preeclampsia, HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), hyperemesis gravidarum, acute fatty liver of pregnancy, and maternal floor infarct of the placenta. In this review we discuss the biochemical and molecular basis, clinical features, diagnosis, and management of long-chain L-3-hydroxyacyl-coenzyme A dehydrogenase deficiency.

Evidence for fatty acid oxidation in human placenta, and the relationship of fatty acid oxidation enzyme activities with gestational age

Fetal disorders of mitochondrial fatty acid oxidation have recently been associated with obstetric complications including pre-eclampsia, Hemolysis, Elevated Liver enzymes, Low Platelets (HELLP) syndrome, placental floor infarct, and Acute Fatty Liver of Pregnancy (AFLP). These diseases occur in about a third of the mothers who are heterozygous for a defect in long chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) enzyme and who bear a fetus homozygous for the defect. The mechanism of this association is not clearly understood. In this study, we provide evidence that the placenta may be the site of production of toxic intermediates of fatty acid metabolism, which accumulate to cause liver damage in the mother. We show that two critical enzymes of long chain fatty acid metabolism, long chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and short chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD), are active in the normal human placenta. There is an inverse correlation between the enzyme activity of both the enzymes and maternal gestational age during the second and third trimesters. We believe that the demonstration of fatty acid oxidation enzyme activity by the placenta is the first step towards assessing a possible role for fetal/placental fatty acid oxidation defects in the pathogenesis of a subset of pregnancy complications.

Inherited disorders of mitochondrial fatty acid oxidation: a new responsibility for the neonatologist

The disorders of mitochondrial fat oxidation present clinically with three major clinical phenotypes: hypoketotic hypoglycemia, cardiomyopathy, and myopathy. Although these features can present together in some of the disorders, one will be the dominant clinical problem. This review will describe these clinical phenotypes while addressing the diagnostic value of various clinical and laboratory studies which are often used for making these diagnoses. With knowledge of the clinical presentation, these diagnoses can often be made very rapidly and at relatively low cost by more specific laboratory tests. The increasing availability of expanded newborn screening by tandem mass spectrometry as well as prenatal diagnosis for these often fatal disorders now provides the opportunity for pre-symptomatic diagnosis. The neonatologist is now in the unique position of identifying these inherited disorders prior to or during severe symptom onset and has the earliest opportunity to provide successful treatment intervention.

Placental floor infarction complicating the pregnancy of a fetus with long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency

By postmortem biochemical and molecular genetic analyses, an 8-month-old infant was diagnosed with long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency, an inborn error of mitochondrial fatty acid beta-oxidation. He was born following a pregnancy complicated by a maternal floor infarction of the placenta, a disorder of unknown etiology. We speculate that the child's autosomal recessive fatty acid beta-oxidation disorder and the pregnancy complication are causally related.