Inherited long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency and a fetal-maternal interaction cause maternal liver disease and other pregnancy complications

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.

Outcomes and genotype correlations in patients with mitochondrial trifunctional protein or isolated long chain 3-hydroxyacyl-CoA dehydrogenase deficiency enrolled in the IBEM-IS database

Purpose

Mitochondrial trifunctional protein deficiency (TFPD) and isolated long chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) are two related defects of fatty acid β -oxidation. While NBS has decreased mortality, morbidity remains significant. Additionally, the relationship of genotype to clinical outcome remains unclear. To better understand these issues, we collected natural history data for these conditions by reviewing seven years of retrospective data from 45 cases of TFPD or LCHADD in the Inborn Errors of Metabolism - Information System.

Methods

Available data included age at database entry, last datapoint, and development of various complications. Data were analyzed by clinical assigned diagnosis (LCHADD or TFPD), subdivided by method of ascertainment (newborn screening-NBS, or other than by newborn screening-NNBS), then re-analyzed based on four genotype groups: homozygous c.1528GC (p.E510Q) (common LCHAD variant); heterozygous c.1528GC (p.E510Q), other HADHA variants; and HADHB variants.

Results

Forty-five patients from birth to 34 years of age were analyzed by assigned diagnosis (30 LCHADD and 15 TFPD) and method of ascertainment. Thirty had further analysis by genotype (22 biallelic HADHA variants and 8 biallelic HADHB variants). With regards to maternal complications, retinopathy, cardiomyopathy and hypoglycemia, patients with biallelic HADHA variants (with or without the common LCHAD variant) manifest a traditional LCHADD phenotype, while those with HADHB gene variants more commonly reported neuromusculoskeletal type TFPD phenotype. While retinopathy, rhabdomyolysis and peripheral neuropathy tended to present later in childhood, many features including initial report of cardiomyopathy and hypoglycemia presented across a wide age spectrum.

Conclusion

This study demonstrates the utility of genotypic confirmation of patients identified with LCHADD/TFPD as variants in the HADHA and HADHB genes lead to different symptom profiles. In our data, biallelic HAHDA variants conferred a LCHADD phenotype, regardless of the presence of the common LCHAD variant.

Hypoparathyroidism, neutropenia and nephrotic syndrome in a patient with mitochondrial trifunctional protein deficiency: A case report and review of the literature

INTRODUCTION

Mitochondrial trifunctional protein (TFP) deficiency is an autosomal recessive disorder that causes a clinical spectrum of diseases ranging from severe infantile cardiomyopathy to mild chronic progressive neuromyopathy, however, parathyroid glands, hematologic system and kidney damage are not the common presentations of this disease.

METHODS

We describe the clinical, biochemical and molecular features of the TFP deficiency patient at our institution. We also provide an extensive literature review of previous published cases with emphasis on the clinical/biochemical phenotype-genotype correlation of this disorder.

RESULTS

Our case is a complete TFP deficiency patient dominated presented with hypoparathyroidism, neutropenia and nephrotic syndrome, which caused by compound heterozygoues variants in HADHB gene. Based on the retrospective study of 157 cases, TFP patients presented with diverse clinical, biochemical and molecular features. The onset age is typically before early childhood. Neuromuscular system is more vulnerable involved. Severe form is generally characterized by multiorgan involvement. A notable feature of severe and intermediate form is respiratory failure. Neuropathy and rhabdomyolysis are the typical manifestations of mild form. Increased long-chain 3-OH-acylcarnitines (C16-OH, C18:1-OH) are the most common biochemical finding. The mortality of the present study is as high as 57.9%, which is linked with the onset age, phenotype, mutation type and muscular histology. Mutations in HADHB are more frequent in Asian descent with complete TFP deficiency and usually presented with atypical presentations. The type of mutation, rather than residual enzyme activity seem to be more related to the phenotype and prognosis. The most common HADHA variant is 1528G > C, no common HADHB variant were detected.

CONCLUSIONS

TFP deficiency is heterogeneous at both the molecular and phenotypic levels, generally a high mortality. Although there is no strict clinical/biochemical phenotype-genotype correlation, difference in ethnic and subunit mutations still have certain characteristics.

Acute Fatty Liver of Pregnancy

Acute fatty liver of pregnancy is a rare, but potentially fatal obstetric disorder characterized principally by varying degrees of hepatic failure with an onset typically in late pregnancy. This review outlines the etiopathogenesis and describes the multiorgan involvement that often results in a number of clinical and laboratory aberrations. These laboratory derangements provide distinct features to differentiate from other obstetric complications, such as hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome. Once recognized, central to the management of acute fatty liver of pregnancy is delivery planning and meticulous supportive care. One particularly dangerous complication is profound coagulopathy. After delivery, the coagulation defect resolves over 1-2 days, and hepatic and renal function are restored soon thereafter. This report offers anticipated recovery and management strategies for commonly associated complications. Application of these factors has served to decrease mortality from as high as 80% down to 10%; however, given the seriousness of this condition, severe maternal morbidities are frequently associated with this obstetric emergency.

Acute Liver Failure (ALF) in Pregnancy: How Much Is Pregnancy Related?

BACKGROUND AND AIMS

Acute liver failure (ALF), characterized by sudden onset of coagulopathy (international normalized ratio [INR] ≥ 1.5) and encephalopathy, may occur during pregnancy either as a pregnancy-associated etiology or an unrelated and coincidental liver injury. The U.S. Acute Liver Failure Study Group, comprised of 33 tertiary care liver centers, has enrolled consecutive patients with ALF or acute liver injury (ALI; INR ≥ 2.0 with no encephalopathy), over two decades.

APPROACH AND RESULTS

Etiologies, clinical features, and outcomes of 70 of 3,155 patients (2.2%) who developed ALF or ALI during pregnancy were reviewed to determine how many were pregnancy associated (pregnancy-associated liver disease; PAALD) and how many were attributed to other etiologies. Thirty-five of the 70 were considered PAALD, of whom nearly half were attributed to hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome and half to acute fatty liver of pregnancy (AFLP), although, in some instances, the distinction was unclear. Virtually all with PAALD had been delivered before hepatology referral, mostly by cesarean section. Acetaminophen toxicity accounted for 21 (60% of the remaining cases), with the remainder resulting from a variety of other causes, but not including viral hepatitis A through E. Although recovery with delivery or supportive measures was possible in most cases, 11 of 70 (16%) required liver transplantation and 8 (11%) died. Swansea criteria to diagnose AFLP were met by all patients with PAALD and also by virtually all women with other forms of ALF.

CONCLUSIONS

Only half of those with ALF during pregnancy appeared to have HELLP or AFLP. Morbidity and mortality for mother and fetus are strongly associated with etiology of liver failure.

Acute Fatty Liver of Pregnancy: Pathophysiology, Anesthetic Implications, and Obstetrical Management

A narrative review of the pathophysiology, diagnosis, management, delivery implications, obstetric anesthesia care, and potential critical care needs in patients presenting with acute fatty liver of pregnancy.

Neonatal screening in the Czech Republic: increased prevalence of selected diseases in low birthweight neonates

Neonates with low birthweight (LBW) represent a vulnerable population. This retrospective study analyzed the birth frequency of diseases detected by neonatal screening (NBS) in normal and LBW neonates in the Czech Republic. Between years 2002 and 2016, the number of screened disorders in the Czech Republic gradually increased from two to 13. Prevalence of screened diseases was calculated for cohorts ranging from 777,100 to 1,277,283 neonates stratified by birthweight. Odds ratio of the association of LBW with each disease was calculated and statistical significance was evaluated using the chi-square test or Fisher's exact test, as appropriate. Three diseases were associated with higher risk of prevalence in LBW neonates, namely congenital hypothyroidism (OR 2.50, CI 1.92; 3.25), cystic fibrosis (OR 2.44, CI 1.51; 3.94), and long chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) (OR 7.74, CI 2.18; 27.42).Conclusion: Although the underlying mechanisms are not well understood, results can be hypothesized that LBW (respectively prematurity) may lead to the secondary and often transitory hypothyroidism while cystic fibrosis and LCHADD may manifest already prenatally and result into preterm birth and LBW. What is Known: • The percentage of low birthweight (LBW) neonates in the Czech Republic has been increasing. • Previously published studies reported positive association between LBW and congenital hypothyroidism and cystic fibrosis. What is New: • The association between LCHADD and LBW has not yet been described. • LBW can be the first manifestation of cystic fibrosis and LCHADD.

Fatal pitfalls in newborn screening for mitochondrial trifunctional protein (MTP)/long-chain 3-Hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency

Background

Mitochondrial trifunctional protein (MTP) and long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency are long-chain fatty acid oxidation disorders with particularly high morbidity and mortality. Outcome can be favorable if diagnosed in time, prompting the implementation in newborn screening programs. Sporadic cases missed by the initial screening sample have been reported. However, little is known on pitfalls during confirmatory testing resulting in fatal misconception of the diagnosis.

Results

We report a series of three patients with MTP and LCHAD deficiency, in whom diagnosis was missed by newborn screening, resulting in life-threatening metabolic decompensations within the first half year of life. Two of the patients showed elevated concentrations of primary markers C16-OH and C18:1-OH but were missed by confirmatory testing performed by the maternity clinic. A metabolic center was not consulted. Confirmatory testing consisted of analyses of acylcarnitines in blood and organic acids in urine, the finding of normal excretion of organic acids led to rejection and underestimation of the diagnosis, respectively. The third patient, a preterm infant, was not identified in the initial screening sample due to only moderate elevations of C16-OH and C18:1-OH and normal secondary markers and analyte ratios.

Conclusion

Our observations highlight limitations of newborn screening for MTP/LCHAD deficiency. They confirm that analyses of acylcarnitines in blood and organic acids in urine alone are not suitable for confirmatory testing and molecular or functional analysis is crucial in diagnosing MTP/LCHAD deficiency. Mild elevations of primary biomarkers in premature infants need to trigger confirmatory testing. Our report underscores the essential role of specialized centers in confirming or ruling out diagnoses in suspicious screening results.

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.

Management of an LCHADD Patient During Pregnancy and High Intensity Exercise

In this report we describe a female Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase Deficiency (LCHADD) patient who suffered from severe exercise intolerance. At age 34, the patient became pregnant for the first time. After an uneventful first 32 weeks of pregnancy she developed sinus tachycardia (resting heart rate 120-134 bpm) and lactate and creatinine kinase levels increased (3.3 mmol/L and 264 U/L, respectively). Increasing MCT supplementation (dose and frequency of administration) lowered heart rate and improved biochemical parameters. At 34 weeks the heart rate rose again and it was decided to deliver the child by caesarean section. Postpartum both mother and child did well.Prior to pregnancy, she performed exercise tests with different doses of medium chain triglycerides (MCTs) to establish a safe and effective exercise program (baseline test, second test with 10 g MCTs and third test with 20 g of MCTs). In the MCT supplemented tests the maximal power output was 23% (second test) and 26% (third test) higher, while cardiac output at maximal power output was the same in all three tests (~15.8 L/min).In conclusion, this is the first report of pregnancy in an LCHADD patient, with favourable outcome for both mother and child. Moreover, in the same patient, MCT supplementation improved cardiac performance and metabolic parameters during high intensity exercise. Using impedance cardiography, we got a clear indication that this benefit was due to improved muscle energy generation at high intensity exercise, since at the same cardiac output a higher power output could be generated.

The phenotypic spectrum of organic acidurias and urea cycle disorders. Part 1: the initial presentation

BACKGROUND

The clinical presentation of patients with organic acidurias (OAD) and urea cycle disorders (UCD) is variable; symptoms are often non-specific.

AIMS/METHODS

To improve the knowledge about OAD and UCD the E-IMD consortium established a web-based patient registry.

RESULTS

We registered 795 patients with OAD (n = 452) and UCD (n = 343), with ornithine transcarbamylase (OTC) deficiency (n = 196), glutaric aciduria type 1 (GA1; n = 150) and methylmalonic aciduria (MMA; n = 149) being the most frequent diseases. Overall, 548 patients (69 %) were symptomatic. The majority of them (n = 463) presented with acute metabolic crisis during (n = 220) or after the newborn period (n = 243) frequently demonstrating impaired consciousness, vomiting and/or muscular hypotonia. Neonatal onset of symptoms was most frequent in argininosuccinic synthetase and lyase deficiency and carbamylphosphate 1 synthetase deficiency, unexpectedly low in male OTC deficiency, and least frequently in GA1 and female OTC deficiency. For patients with MMA, propionic aciduria (PA) and OTC deficiency (male and female), hyperammonemia was more severe in metabolic crises during than after the newborn period, whereas metabolic acidosis tended to be more severe in MMA and PA patients with late onset of symptoms. Symptomatic patients without metabolic crises (n = 94) often presented with a movement disorder, mental retardation, epilepsy and psychiatric disorders (the latter in UCD only).

CONCLUSIONS

The initial presentation varies widely in OAD and UCD patients. This is a challenge for rapid diagnosis and early start of treatment. Patients with a sepsis-like neonatal crisis and those with late-onset of symptoms are both at risk of delayed or missed diagnosis.

Gestational Diabetes Associated with a Novel Mutation (378-379insTT) in the Glycerol Kinase Gene

Glycerol kinase deficiency (GKD) is an X-linked inborn error of metabolism at the interface of fat and carbohydrate metabolism. We report a male patient with GKD and a novel insertion of TT in exon 5 at position 378 of the GK cDNA (378–379insTT). This resulted in a premature stop codon and 0.8% normal GK activity. The mother is a carrier for this mutation and had gestational diabetes requiring insulin during this pregnancy but not in her previous pregnancy. Given the association between GKD and type 2 diabetes mellitus, it is interesting that the mother had gestational diabetes while carrying an affected fetus. Therefore, GKD is another disease where there may be a maternal–fetal interaction based on genotype. Further investigations may help elucidate the role of GKD in the carrier mother's gestational diabetes. In addition, these studies will provide better-informed counseling to families with GKD regarding the risk to carrier females.

Medical Problems in Obstetrics: Inherited Metabolic Disease

An increasing number of women with rare inherited disorders of metabolism are becoming pregnant. Although, in general, outcomes for women and their children are good, there are a number of issues that need to be considered. Currently, limited specific guidance on the management of these conditions in pregnancy is available. Prepregnancy counselling with information on inheritance, options for reproduction, teratogenicity risk, potential impact on maternal health and long-term health of children should be offered. With appropriate specialist management, the teratogenic risk of conditions such as maternal phenylketonuria (PKU) can be eliminated, and the risk of metabolic decompensation in disorders of energy metabolism or intoxication significantly reduced. Multidisciplinary management, and close liaison between obstetricians and other specialists, is required for those women in whom there is cardiac, renal, respiratory, joint or other organ involvement.

Pregnancy in women with inherited metabolic disease

An increasing number of women with rare inherited disorders of metabolism are becoming pregnant. Whilst, in general, outcomes for women and their children are good, there are issues that need to be considered. Due to the rarity of many conditions, there is limited specific guidance available on best management. Prepregnancy counselling with information on inheritance, options for reproduction, teratogenicity risk, potential impact on maternal health and long-term health of children should be offered. With appropriate specialist management, the teratogenic risk of conditions such as maternal phenylketonuria (PKU) can be eliminated, and the risk of metabolic decompensation in other disorders of intoxication or energy metabolism significantly reduced. Newer therapies, such as enzyme replacement therapy, appear to be safe in pregnancy, but specific advice should be sought. Multidisciplinary management, and close liaison between obstetricians and other specialists is required for women in whom there is cardiac, renal, respiratory, joint or other organ involvement.

Clinical outcome, biochemical and therapeutic follow-up in 14 Austrian patients with Long-Chain 3-Hydroxy Acyl CoA Dehydrogenase Deficiency (LCHADD)

Background

LCHADD is a long-fatty acid oxidation disorder with immediate symptoms and long-term complications. We evaluated data on clinical status, biochemical parameters, therapeutic regimens and outcome of Austrian LCHADD patients.

Study design

Clinical and outcome data including history, diagnosis, short- and long-term manifestations, growth, psychomotor development, hospitalizations, therapy of 14 Austrian patients with LCHADD were evaluated. Biochemically, we evaluated creatine kinase (CK) and acyl carnitine profiles.

Results

All LCHADD patients are homozygous for the common mutation. Three are siblings. Diagnosis was first established biochemically. Nine/14 (64%) were prematures, with IRDS occurring in six. In nine (64%), diagnosis was established through newborn screening, the remaining five (36%) were diagnosed clinically. Four pregnancies were complicated by HELLP syndrome, one by preeclampsia. In two, intrauterine growth retardation and placental insufficiency were reported. Five were diagnosed with hepatopathy at some point, seven with cardiomyopathy and eight with retinopathy, clinically relevant only in one patient. Polyneuropathy is only present in one. Three patients have a PEG, one is regularly fed via NG-tube. Growth is normal in all, as well as psychomotor development, except for two extremely premature girls. In 11 patients, 165 episodes with elevated creatine kinase concentrations were observed with 6-31 (median 14) per patient; three have shown no elevated CK concentrations. Median total carnitine on therapy was 19 μmol/l (range 11-61). For 14 patients, there have been 181 hospitalizations (median 9 per patient), comprising 1337 in-patient-days. All centres adhere to treatment with a fat-defined diet; patients have between 15% and 40% of their energy intake from fat (median 29%), out of which between 20% and 80% are medium-chain triglycerides (MCT) (median 62%). Four patients have been treated with heptanoate (C7).

Conclusion

Our data show LCHADD outcome can be favourable. Growth and psychomotor development is normal, except in two prematures. Frequency of CK measurements decreases with age, correlating with a decreasing number of hospitalizations. About 50% develop complications affecting different organ systems. There is no relevant difference between the patients treated in the respective centers. Concluding from single case reports, anaplerotic therapy with heptanoate should be further evaluated.

Depleted mitochondrial DNA content in peripheral blood of women with a history of HELLP syndrome

OBJECTIVE

To test the hypothesis that a quantitative defect of maternal cellular mitochondria would play a role in the pathogenesis of HELLP syndrome.

STUDY DESIGN

Peripheral blood mitochondrial DNA (MtDNA) was measured in 20 non-pregnant women with a history of HELLP syndrome, 40 non-pregnant control subjects who had previous physiologic pregnancies, 59 subjects carrying physiologic pregnancies, seven pregnant women with a history of HELLP syndrome and five women in the active phase of the disease.

MAIN OUTCOME MEASURE

Peripheral blood Mt-DNA.

RESULTS

The median (interquartile range) mtDNA in women with a history of HELLP syndrome, in non-pregnant women who had previous physiologic pregnancies, in subjects carrying physiologic pregnancies, in pregnant women with a history of HELLP syndrome and in women in the active phase of the disease was 115 (81-194), 229 (199-319), 174 (136-211), 101 (82-178) and 92 (39-129) copies per nuclear DNA, respectively. Non-pregnant women with a history of HELLP syndrome had significantly lower levels than non-pregnant controls (p<0.001). Moreover, blood mtDNA was lower in pregnant women with a history of HELLP syndrome and in those in the active phase of the disease when compared to pregnant controls (p=0.002 and p=0.025, respectively).

CONCLUSIONS

Attenuated maternal mitochondrial function may favor HELLP syndrome development.

Decreased mitochondrial fatty acid oxidation in placentas from women with preeclampsia

Preeclampsia is a leading cause of maternal and fetal morbidity and mortality in high and low-income countries. The aetiology of preeclampsia is multifactorial and remains obscure. Some evidences suggest that altered placental fatty acid oxidation might play a role in the pathogenesis of preeclampsia. To reveal if placental fatty acid oxidation is reduced in preeclampsia, we evaluate the expression levels of enzymes of mitochondrial fatty acid oxidation using quantitative Real-time PCR and the fatty acid oxidation rate in placental explants. We found that long-chain 3-hydroxyacyl-CoA dehydrogenase levels and fatty acid oxidation capacity were significantly reduced in placentas from women with preeclampsia.

Impact of selected inborn errors of metabolism on prenatal and neonatal development

In general, data regarding maturational processes of different metabolic pathways in the very vulnerable fetal and neonatal period are rare. This review is to substantiate the impact of selected inborn errors of metabolism on this critical period of life and their clinical manifestation. Significant adaptation of mitochondrial/energy-, carbohydrate-, lysosomal-, and amino acid-metabolism occurs during early prenatal and neonatal development. In utero, metabolic environment has an impact on the development of the fetus as well as fetal organ maturation. Defects of distinct metabolic pathways could therefore already be of significant relevance in utero and for clinical manifestations in the early fetal and neonatal period. Disturbances of these pathways may influence intrauterine growth and health. Production of a toxic intrauterine milieu, energy-deficiency, modification of membrane function, or disturbance of the normal intrauterine expression of genes may be responsible for fetal compromise and developmental disorders. Three categories of metabolic disorders will be discussed: the "intoxication type" (classical galactosemia, ornithine transcarbamylase deficiency, and "maternal phenylketonuria"), the "storage type" (Morbus Niemann Pick type C), and the "energy deficient type" (including long-chain fatty acid oxidation disorders, pyruvate dehydrogenase deficiency, and respiratory chain defects). For these disorders, the pathophysiology of early manifestation, special aspects regarding the prenatal and neonatal period, and diagnostic as well as therapeutic options are presented.

Preeclampsia and HELLP syndrome: impaired mitochondrial function in umbilical endothelial cells

Preeclampsia (PE) and hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome have been linked to congenital fetal disorders of mitochondrial fatty acid oxidation (FAO). Different incidences may argue for the association of noncongenital alterations of mitochondrial energy metabolism with PE/HELLP syndrome. We studied human umbilical vein endothelial cells [HUVEC] as selected part of the feto-placental unit from uncomplicated (n = 46) and diseased (n = 27; 17 PE and 10 HELLP) pregnancies by measuring the overall FAO, carnitine palmitoyltransferase 2 (CPT2), respiratory chain (RC) complexes I-V, citratesynthase (CS), lactatedehydrogenase (LDH), hexokinase (HK), phosphofructokinase (PFK), and energy rich phosphates. Maternal and infantile acylcarnitines in blood were investigated post partum. Overall FAO, RC complexes II-V, and CS were significantly compromised in HUVEC from complicated pregnancies; impairment of complexes I + III was not significant. CPT2 and energy charges were unaffected. Lactatedehydrogenase and PFK from complicated pregnancies were upregulated, and HK remained constant. In blood, carnitine was elevated in diseased women and their children, acylcarnitines were higher in affected infants. Impaired mitochondrial function in HUVEC is associated with PE/HELLP syndrome and may be involved in the pathophysiology of these diseases.

Current concepts of mechanisms in drug-induced hepatotoxicity

Drug-induced liver injury (DILI) has become a leading cause of severe liver disease in Western countries and therefore poses a major clinical and regulatory challenge. Whereas previously drug-specific pathways leading to initial injury of liver cells were the main focus of mechanistic research and classifications, current concepts see these as initial upstream events and appreciate that subsequent common downstream pathways and their attenuation by drugs and other environmental and genetic factors also have a profound impact on the risk of an individual patient to develop overt liver disease. This review summarizes current mechanistic concepts of DILI in a 3-step model that limits its principle mechanisms to three main ways of initial injury, i.e. direct cell stress, direct mitochondrial impairment, and specific immune reactions. Subsequently, initial injury initiates further downstream events, i.e. direct and death receptor-mediated pathways leading to mitochondrial permeability transition, which then results in apoptotic or necrotic cell death. For all mechanisms, mitochondria play a central role in events leading to apoptotic vs. necrotic cell death. New treatment targets consequently focus on interference with downstream pathways that mediate injury and therefore determine the ultimate outcome of DILI. Genome wide and targeted pharmacogenetic as well as metabonomic approaches are now used in order to reach the key goals of a better understanding of mechanisms in hepatotoxicity, and to develop new strategies for its prediction and treatment. However, the complexity of interactions between genetic and environmental risk factors is considerable, and DILI therefore currently remains unpredictable for most hepatotoxins.

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.

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.

Neither maternal nor fetal mutation (E474Q) in the alpha-subunit of the trifunctional protein is frequent in pregnancies complicated by HELLP syndrome

OBJECTIVE

An association between maternal HELLP syndrome and fetal long chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency has been proposed. LCHAD catalyzes the third step in the beta-oxidation of fatty acids in mitochondria. Whereas about 75% of LCHAD-deficient patients carry a G-to-C mutation at nucleotide position 1528 (Glu474Gln, E474Q) on both chromosomes, compound heterozygosity for E474Q on one chromosome and a second different LCHAD mutation on the other can be observed in up to 25% of LCHAD-deficiency cases; only very few patients carry two mutations different from E474Q. Genetic analysis of the mother alone is insufficient in case of compound heterozygosity. Since information on the fetal carrier status of the E474Q mutation in maternal HELLP syndrome is rare, we investigated the frequency of the E474Q mutation in families where the mother had HELLP syndrome.

METHODS

The occurrence of the E474Q mutation was analyzed by PCR and RFLP in 103 mothers with HELLP syndrome, in 82 children of affected pregnancies and in 21 fathers in families where fetal DNA was not available. In addition, 103 control women with only uncomplicated pregnancies were investigated.

RESULTS

The mutation E474Q was not detected in the study population.

CONCLUSION

Neither maternal nor fetal heterozygosity for the E474Q mutation is a relevant factor of HELLP syndrome.

Understanding and managing HELLP syndrome: the integral role of aggressive glucocorticoids for mother and child

Antepartum or postpartum HELLP syndrome constitutes an obstetric emergency that requires expert knowledge and management skills. The insidious and variable nature of disease presentation and progression challenges the clinician and complicates consensus on universally accepted diagnostic and classification criteria. A critical review of published research about this variant form of severe preeclampsia, focused primarily on what is known about the pathogenesis of this disorder as it relates to patient experience with corticosteroids for its management, leads to the conclusion that there is maternal-fetal benefit realized when potent glucocorticoids are aggressively used for its treatment. Although acknowledging the need for definitive multicenter trials to better define the limits of benefit and the presence of any maternal or fetal risk, and given an understanding of the nature of the disorder with its potential to cause considerable maternal morbidity and mortality, we recommend for the present that aggressively used potent glucocorticoids constitute the cornerstone of management for patients considered to have HELLP syndrome.

Identification of a novel single nucleotide polymorphism of HADHA gene at a referred primer-binding site during pre-diagnostic tests for preimplantation genetic diagnosis

The pre-diagnostic test for preimplantation genetic diagnosis (PGD) of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency was performed by polymerase chain reaction (PCR) and direct sequencing for hydroxyacyl-Coenzyme A dehydrogenase/3-ketoacyl-Coenzyme A thiolase/enoyl-Coenzyme A hydratase (HADHA) gene. We obtained unexpected genotyping results of HADHA gene by allele drop-out in the analysis of patients' genomic DNA samples with a referred PCR primer set. Upon further analysis with a re-designed primer set, we found a novel single nucleotide polymorphism (SNP) at the referred primer-binding site in the normal allele of HADHA gene (NT_022184, 5233296 a>t). We found that the frequency of this novel SNP was 0.064 in Korean population. Pre-diagnostic test using single lymphocytes and clinical PGD were successfully performed with the re-designed primer set. Nineteen embryos (95.0%) among 20 were successfully diagnosed to 5 homozygous mutated, 8 heterozygous carrier and 6 wild type. Among 6 normal embryos, well developed and selected 4 embryos were transferred into the mother's uterus, but a pregnancy was not achieved. We proposed that an unknown SNP at primer-binding sites would be a major cause of allele drop-out in the PGD for single gene dis-order.

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.

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.

The Association Between Acute Fatty Liver of Pregnancy and Fatty Acid Oxidation Disorders

Acute fatty liver of pregnancy is a relatively rare but potentially fatal liver disorder of late pregnancy. Recent advances in molecular diagnostic procedures provide evidence of a genetic basis for this condition and a link to offspring disorders in fatty acid oxidation. This relationship implies the need for genetic testing and follow-up of at-risk women and their neonates.

Disrupted blastocoele formation reveals a critical developmental role for long-chain acyl-CoA dehydrogenase

Long-chain acyl-CoA dehydrogenase (LCAD) deficiency has not been found in human patients. There has been an LCAD deficient (LCAD-/-) mouse model developed via gene targeting strategies that has gestational loss as a part of its phenotype. We tested the hypothesis that LCAD deficiency disrupts normal embryonic development and explains at least in part the gestational loss in the mouse and may suggest a mechanism to explain the lack of any human patients with this inherited enzyme deficiency. We cultured and evaluated embryos with three different genotypes: LCAD+/+, LCAD+/-, and LCAD-/-. We found a significantly increased rate of death (P<0.012) in LCAD-/- embryos at the morula-to-blastocyst conversion indicating a deficient ability to complete the development of a blastocoele and formation of a blastocyst. Furthermore, we hypothesized that we could rescue LCAD-/- embryos in culture by supplying excess fatty acids of chain-lengths that could be readily oxidized by them despite their inherited enzyme deficiency. We were unable, however, to demonstrate any rescue by supplementing the culture medium with fatty acids of a wide-range of chain-lengths. Therefore, overall we demonstrated a severely deficient capacity for LCAD-/- embryos to develop past the morula stage with intermediate rates of development found in the LCAD+/- embryos as compared to the LCAD+/+ embryos. Furthermore, we were unable to rescue the LCAD-/- embryos with any fatty acid supplementation.

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.

Absence of the G1528C (E474Q) mutation in the alpha-subunit of the mitochondrial trifunctional protein in women with acute fatty liver of pregnancy

Acute fatty liver of pregnancy (AFLP) is a rare and dreaded complication of pregnancy, almost exclusively seen in the third trimester. The histopathologic features of AFLP closely resemble those seen in metabolic disorders characterized by deficiency of fatty acid oxidative enzymes. Several reports have established a strong association between AFLP in the mother and fetal deficiency of the enzyme long-chain L-3-hydroxyacyl-CoA dehydrogenase (LCHAD). However, these studies have an inevitable selection bias resulting from ascertainment through an affected infant, rather than an unselected population of patients with AFLP. We retrospectively examined a series of 10 women with pregnancies complicated by AFLP to determine the prevalence of the common LCHAD mutation (G1528C) in this population. The existing LCHAD primers, which produce a 640-bp amplicon (IJlst L, Ruiter JP, Hoovers JM, Jakobs ME, Wanders RJ: J Clin Invest 98:1028-1033, 1996), were modified to make them amenable to analysis of fragmented DNA obtained from microdissected formalin-fixed material. None of the patients were found to harbor the common G1528C mutation. It is likely that AFLP arising in the context of fetal LCHAD deficiency represents only one of the possible etiologies for this uncommon disorder, and the metabolic basis of AFLP is more heterogeneous than previously believed.

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: clinical presentation and follow-up of 50 patients

OBJECTIVES

To assess the mode of presentation, biochemical abnormalities, clinical course, and effects of therapy in patients of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency.

BACKGROUND

LCHAD deficiency is a rare, autosomal recessive inborn error of fatty acid oxidation. Although case reports and small series of patients have been published, these may not give a true picture of the clinical and biochemical spectrum associated with this disorder. To improve the early recognition and management of this potentially lethal disorder, we have reviewed a large cohort of LCHAD-deficient patients.

METHODS

A questionnaire was sent to the referring physicians of 61 unselected patients with LCHAD deficiency diagnosed in our center. The standardized questionnaire requested information about the clinical signs and symptoms at presentation, the clinical history, family history, pregnancy, biochemical parameters at presentation, treatment, and clinical outcome.

RESULTS

Questionnaires on 50 patients (82%) were returned and included in this study. The mean age of clinical presentation was 5.8 months (range: 1 day-26 months). Seven (15%) of the patients presented in the neonatal period. Thirty-nine patients (78%) presented with hypoketotic hypoglycemia, the classical features of a fatty acid oxidation disorder. Eleven patients (22%) presented with chronic problems, consisting of failure to thrive, feeding difficulties, cholestatic liver disease, and/or hypotonia. In retrospect, most (82%) of the patients presenting with an acute metabolic derangement also suffered from a combination of chronic nonspecific symptoms before the metabolic crises. Mortality in this series was high (38%), all dying before or within 3 months after diagnosis. Morbidity in the surviving patients is also high, with recurrent metabolic crises and muscle problems despite therapy.

CONCLUSIONS

LCHAD deficiency often presents with a combination of chronic nonspecific symptoms. Early diagnosis is difficult in the absence of the classical metabolic derangement. Survival can be improved by prompt diagnosis, but morbidity remains alarmingly high despite current therapeutic regimes.

Glutamate 170 of human l-3-hydroxyacyl-CoA dehydrogenase is required for proper orientation of the catalytic histidine and structural integrity of the enzyme

l-3-Hydroxyacyl-CoA dehydrogenase (HAD), the penultimate enzyme in the beta-oxidation spiral, reversibly catalyzes the conversion of l-3-hydroxyacyl-CoA to the corresponding 3-ketoacyl-CoA. Similar to other dehydrogenases, HAD contains a general acid/base, His(158), which is within hydrogen bond distance of a carboxylate, Glu(170). To investigate its function in this catalytic dyad, Glu(170) was replaced with glutamine (E170Q), and the mutant enzyme was characterized. Whereas substrate and cofactor binding were unaffected by the mutation, E170Q exhibited diminished catalytic activity. Protonation of the catalytic histidine did not restore wild-type activity, indicating that modulation of the pK(a) of His(158) is not the sole function of Glu(170). The pH profile of charge transfer complex formation, an independent indicator of active site integrity, was unaltered by the amino acid substitution, but the intensity of the charge transfer band was diminished. This observation, coupled with significantly reduced enzymatic stability of the E170Q mutant, implicates Glu(170) in maintenance of active site architecture. Examination of the crystal structure of E170Q in complex with NAD(+) and acetoacetyl-CoA (R = 21.9%, R(free) = 27.6%, 2.2 A) reveals that Gln(170) no longer hydrogen bonds to the side chain of His(158). Instead, the imidazole ring is nearly perpendicular to its placement in the comparable native complex and no longer positioned for efficient catalysis.

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

There is a correlation between pregnancy complications such as acute fatty liver of pregnancy and long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency. We diagnosed another fatty acid beta-oxidation defect, short-chain acyl-coenzyme A dehydrogenase deficiency, in an infant when evaluating him because his mother had acute fatty liver of pregnancy. Other beta-oxidation defects, in addition to LCHAD deficiency, should be considered in children born after pregnancies complicated by liver disease.

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.

Molecular prenatal diagnosis in families with fetal mitochondrial trifunctional protein mutations

OBJECTIVES

To evaluate the feasibility of molecular prenatal diagnosis in families with mitochondrial trifunctional protein (TFP) mutations and prospectively study the effects of fetal genotype on pregnancy outcome. TFP catalyzes the last 3 steps in mitochondrial long-chain fatty acid oxidation.

STUDY DESIGN

We performed molecular prenatal diagnosis in 9 pregnancies, 8 in 6 families with isolated long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency and one in a family with complete TFP deficiency. Analyses were performed on chorionic villous samples in 7 pregnancies and on amniocytes in 2.

RESULTS

Molecular prenatal diagnosis successfully identified the fetal genotype in all 9 pregnancies. Two fetuses were affected, and both pregnancies were terminated by family decision. Two other fetuses had normal genotype and 5 others were heterozygotes. These 7 pregnancies were uncomplicated, and all the offspring are alive and apparently healthy. Genotypes of the aborted fetuses and neonates were confirmed by molecular analysis and enzymatic assays.

CONCLUSIONS

Molecular prenatal diagnosis is possible and valid in guiding management of pregnancies in families with known TFP defects. Women heterozygous for TFP alpha-subunit mutations who carry fetuses with wild-type or heterozygous genotypes have uncomplicated pregnancies.

Trifunctional protein deficiency: three families with significant maternal hepatic dysfunction in pregnancy not associated with E474Q mutation

We report five families with trifunctional protein deficiency in which, during pregnancy, three mothers experienced significant hepatic disease when carrying an affected fetus. Diagnoses were based on increased levels of long-chain hydroxyacylcarnitines and deficiencies of 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and 3-ketoacyl-CoA thiolase activity in fibroblasts. All affected infants lacked the common E474Q mutation associated with isolated LCHAD deficiency. This mutation is thought to be a predisposing factor for maternal hepatic disease in pregnancy. Our findings suggest that other defects in this enzyme complex might be responsible for maternal hepatic complications in pregnancy.

Disorders of fatty acid transport and mitochondrial oxidation: challenges and dilemmas of metabolic evaluation

Inborn errors of fatty acid transport and mitochondrial oxidation (FATMO) have drawn considerable attention in recent years for the rapid pace of discovery of new defects and an ever-increasing spectrum of clinical phenotypes. Several of these disorders are not detected by conventional biochemical investigations, even when a patient is symptomatic with fasting intolerance or functional failure of fatty acid dependent tissue(s). In our view, today's major challenges are the inclusion of FATMO disorders in newborn screening programs and the investigation of the role played by individual disorders in maternal complications of pregnancy, sudden and unexpected death in early life, and pediatric acute/fulminant liver failure. Dilemmas are found in the debate over the limitations, if any, to be imposed on the expansion of newborn screening using tandem mass spectrometry, in the provision of prenatal diagnosis for otherwise treatable disorders, and in the diagnostic workup of "unclassified" cases.

New developments in the pathophysiology, clinical spectrum, and diagnosis of disorders of fatty acid oxidation

Fatty acid oxidation disorders are among the most common inborn errors of metabolism affecting infants and children. Recognition of this family of defects is critical because careful dietary monitoring, avoidance of fasting, and prompt intervention during common childhood illness can prevent catastrophic cardiac and metabolic decompensation. This review focuses on new molecular and clinical diagnostic aspects of several of these disorders. Recent papers highlight the recognition that the clinical spectrum of disorders of fatty acid oxidation goes far beyond the stereotypical Reyes-like presentation or cardiomyopathy, and now encompasses more cases of sudden infant death syndrome, fulminant hepatic failure, and severe complications during pregnancy.

Acylcarnitines in plasma and blood spots of patients with long-chain 3-hydroxyacyl-coenzyme A dehydrogenase defiency

The acylcarnitines in plasma and blood spots of 23 patients with proven deficiency of long-chain 3-hydroxyacylcoenzyme A dehydrogenase were reviewed. Long-chain 3-hydroxyacylcarnitines of C14:1, C14, C16 and C18:1 chain length, and long-chain acylcarnitines of C12, C14:1, C14, C16, C18:2 and C18:1 chain length were elevated. Acetylcarnitine was decreased. In plasma, elevation of hydroxy-C18:1 acylcarnitine over the 95th centile of controls, in combination with an elevation of two of the three acylcarnitines C14, C14:1 and hydroxy-C16, identified over 85% of patients with high specificity (less than 0.1% false positive rate). High endogenous levels of long-chain acylcarnitines in normal erythrocytes reduced the diagnostic specificity in blood spots compared with plasma samples. The results were also diagnostic in asymptomatic patients, and were not influenced by genotype. Treatment with diet low in fat and high in medium-chain triglyceride decreased all disease-specific acylcarnitines, often to normal, suggesting that this assay is useful in treatment monitoring.

Inborn errors of metabolism and pregnancy

An increasing number of women with inborn errors of metabolism are now reaching child-bearing age. For certain disorders there are maternal risks associated with pregnancy. These may be related to an increased likelihood of metabolic decompensation (e.g. disorders of the urea cycle) or to increased stress to systems already compromised by disease (e.g. cardiomyopathy in GSD III). Detrimental effects upon the fetus may also be caused by maternal disease, as occurs with phenylketonuria, or from medication used to treat the mother's condition. Less commonly, fetal inborn errors may adversely effect the mother's health--e.g. fetal long-chain acyl-CoA dehydrogenase deficiency and the maternal HELLP syndrome (haemolysis, elevated liver enzymes and low platelets) and AFLP (acute fatty liver of pregnancy). Because of the rarity of individual disorders, our knowledge of risks associated with pregnancy is limited. Even for more common inborn errors such as phenylketonuria, there remain a number of questions that have not been fully answered.

Inborn errors of mitochondrial fatty acid oxidation

Inborn errors of the mitochondrial beta-oxidation of long-chain fatty acids represent an evolving field of inherited metabolic disease. Fatty acid oxidation defects demonstrate an abnormal response to the process of fasting adaptation and affect those tissues that utilize fatty acids as an energy source. These tissues include cardiac and skeletal muscle and liver. Muscle directly uses fatty acids as an energy source whilst hepatic metabolism of fatty acids is mostly directed toward the synthesis of ketone bodies for energy utilization by tissues such as brain. The clinical phenotypes of fatty acid oxidation disorders include disease of one or more of these fatty acid-metabolizing tissues. In this review, we provide an overview of the pathway, discuss the disorders that are well established, and describe recent advances in the field. Currently available diagnostic procedures are critically evaluated.

Neonatal presentations of mitochondrial metabolic disorders

Because of the high energy requirements of the growing neonate, disorders of mitochondrial metabolism caused by defects in fatty acid oxidation, pyruvate metabolism, and the respiratory chain may often present in the neonatal period. Common neonatal presentations are hypotonia, lethargy, feeding and respiratory difficulties, failure to thrive, psychomotor delay, seizures, and vomiting. Laboratory clues include alterations in the levels of lactate, pyruvate (and the lactate/pyruvate ratio), glucose, and ketone bodies. Diagnosis usually depends on specific enzyme assays or on molecular genetic analysis. Without treatment, most infants die in the first few days or months of life. In the last decade, there have been significant advances in the understanding of the molecular basis of these disorders. This review discusses the major subgroups of mitochondrial disorders, focusing on defects of pyruvate oxidation, the Krebs cycle, and the respiratory chain. Disorders caused by respiratory chain defects may involve nuclear DNA, mitochondrial DNA, or intergenomic signaling. Recognition and early diagnosis of these conditions are important in the genetic counseling of these families.