Antenatal manifestations of mitochondrial disorders

Primary Mitochondrial Disorders in the Neonate

Primary mitochondrial disorders (PMDs) are a heterogeneous group of disorders characterized by functional or structural abnormalities in the mitochondria that lead to a disturbance of cellular energy, reactive oxygen species, and free radical production, as well as impairment of other intracellular metabolic functions, causing single- or multiorgan dysfunction. PMDs are caused by pathogenic variants in nuclear and mitochondrial genes, resulting in distinct modes of inheritance. Onset of disease is variable and can occur in the neonatal period, with a high morbidity and mortality. In this article, we review the most common methods used for the diagnosis of PMDs, as well as their prenatal and neonatal presentations. We highlight the shift in the diagnostic approach for PMDs since the introduction of nontargeted molecular tests into clinical practice, which has significantly reduced the use of invasive studies. We discuss common PMDs that can present in the neonate, including general, nonsyndromic presentations as well as specific syndromic disorders. We also review current treatment advances, including the use of mitochondrial "cocktails" based on limited scientific evidence and theoretical reasoning, as well as the impending arrival of personalized mitochondrial-specific treatments.

Endocrine Manifestations and New Developments in Mitochondrial Disease

Mitochondrial diseases are a group of common inherited diseases causing disruption of oxidative phosphorylation. Some patients with mitochondrial disease have endocrine manifestations, with diabetes mellitus being predominant but also include hypogonadism, hypoadrenalism, and hypoparathyroidism. There have been major developments in mitochondrial disease over the past decade that have major implications for all patients. The collection of large cohorts of patients has better defined the phenotype of mitochondrial diseases and the majority of patients with endocrine abnormalities have involvement of several other systems. This means that patients with mitochondrial disease and endocrine manifestations need specialist follow-up because some of the other manifestations, such as stroke-like episodes and cardiomyopathy, are potentially life threatening. Also, the development and follow-up of large cohorts of patients means that there are clinical guidelines for the management of patients with mitochondrial disease. There is also considerable research activity to identify novel therapies for the treatment of mitochondrial disease. The revolution in genetics, with the introduction of next-generation sequencing, has made genetic testing more available and establishing a precise genetic diagnosis is important because it will affect the risk for involvement for different organ systems. Establishing a genetic diagnosis is also crucial because important reproductive options have been developed that will prevent the transmission of mitochondrial disease because of mitochondrial DNA variants to the next generation.

Extremely Rare Case of Fetal Anemia Due to Mitochondrial Disease Managed with Intrauterine Transfusion

This report describes a rare case of fetal anemia, confirmed as a mitochondrial disease after birth, treated with intrauterine transfusion (IUT). Although mitochondrial diseases have been described in newborns, research on their prenatal features is lacking. A patient was referred to our institution at 32 gestational weeks owing to fetal hydrops. Fetal anemia was confirmed by cordocentesis. After IUT had been performed three times, the anemia and associated fetal hydrops showed improvement. However, after birth, the neonate had recurrent pancytopenia and lactic acidosis. He was eventually diagnosed with Pearson syndrome and died 2 months after birth. This is the first case report of fetal anemia associated with mitochondrial disease managed with IUT.

Development of Leigh syndrome with a high probability of cardiac manifestations in infantile-onset patients with m.14453G > A

The m.14453G > A mutation in MT-ND6 has been described in a few patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes or Leigh syndrome.However, the clinical spectrum and molecular characteristics are unclear.Here, we present four infantile-onset patients with m.14453G > A-associated Leigh syndrome. All four patients had brainstem lesions with basal ganglia lesions, and two patients had cardiac manifestations. Decreased ND6 protein expression and immunoreactivity were observed in patient-derived samples. There was no clear correlation between heteroplasmy levels and onset age or between heteroplasmy levels and phenotype; however, infantile onset was associated with Leigh syndrome.

Height as a Clinical Biomarker of Disease Burden in Adult Mitochondrial Disease

CONTEXT

Abnormal growth and short stature are observed in patients with mitochondrial disease, but it is unclear whether there is a relationship between final adult height and disease severity.

OBJECTIVE

To determine whether patients with genetically confirmed mitochondrial disease are shorter than their peers and whether stature is related to disease severity.

DESIGN

Analysis of final adult height in relation to disease severity as determined by the Newcastle Mitochondrial Disease Adult Scale (NMDAS).

SETTING

UK Mitochondrial Disease Patient Cohort (Mito Cohort).

PATIENTS

575 patients were identified with recorded height, weight, and molecular genetic diagnosis of mitochondrial disease within the Mito Cohort.

MAIN OUTCOME MEASURES

Adult height, body mass index (BMI), and their association with genetic subgroup and disease severity.

RESULTS

Adults with mitochondrial disease were short, with a mean height of -0.49 SD (95% CI, -0.58 to -0.39; n = 575) compared with UK reference data. Patients were overweight, with a BMI SD of 0.52 (95% CI, 0.37 to 0.67; n = 472). The most common genetic subgroup (m.3243A>G mutation) had a height SD of -0.70 (95% CI, -0.85 to -0.54; n = 234) and a BMI SD of 0.12 (95% CI, -0.10 to 0.34; n = 212). NMDAS scores were negatively correlated with height SD (r = -0.25; 95% CI, -0.33 to -0.17; P < 0.001, n = 533). Rate of disease progression also correlated negatively with adult height (P < 0.001).

CONCLUSION

Final height in mitochondrial disease reflects disease severity and rate of disease progression. Mitochondrial dysfunction and associated subclinical comorbidities affect growth plate physiology.

Antenatal manifestations of inborn errors of metabolism: prenatal imaging findings

Prenatal manifestations of inborn errors of metabolism (IEM) are related to severe disorders involving metabolic pathways active in the fetal period and not compensated by maternal or placental metabolism. Some prenatal imaging findings can be suggestive of such conditions-especially in cases of consanguinity and/or recurrence of symptoms-after exclusion of the most frequent nonmetabolic etiologies. Most of these prenatal imaging findings are nonspecific. They include mainly ascites and hydrops fetalis, intrauterine growth restriction (IUGR), central nervous system (CNS) anomalies, echogenic kidneys, epiphyseal stippling, craniosynostosis, and a wide spectrum of dysostoses. These anomalies can be isolated, but in most cases, an IEM is suggested by an association of features. It must be stressed that the diagnosis of an IEM in the prenatal period is based on a close collaboration between specialists in fetal imaging, medicine, genetics, biology, and pathology.

Antenatal manifestations of inborn errors of metabolism: biological diagnosis

Inborn errors of metabolism (IEMs) that present with abnormal imaging findings in the second half of pregnancy are mainly lysosomal storage disorders (LSDs), cholesterol synthesis disorders (CSDs), glycogen storage disorder type IV (GSD IV), peroxisomal disorders, mitochondrial fatty acid oxidation defects (FAODs), organic acidurias, aminoacidopathies, congenital disorders of glycosylation (CDGs), and transaldolase deficiency. Their biological investigation requires fetal material. The supernatant of amniotic fluid (AF) is useful for the analysis of mucopolysaccharides, oligosaccharides, sialic acid, lysosphingolipids and some enzyme activities for LSDs, 7- and 8-dehydrocholesterol, desmosterol and lathosterol for CSDs, acylcarnitines for FAODs, organic acids for organic acidurias, and polyols for transaldolase deficiency. Cultured AF or fetal cells allow the measurement of enzyme activities for most IEMs, whole-cell assays, or metabolite measurements. The cultured cells or tissue samples taken after fetal death can be used for metabolic profiling, enzyme activities, and DNA extraction. Fetal blood can also be helpful. The identification of vacuolated cells orients toward an LSD, and plasma is useful for diagnosing peroxisomal disorders, FAODs, CSDs, some LSDs, and possibly CDGs and aminoacidopathies. We investigated AF of 1700 pregnancies after exclusion of frequent etiologies of nonimmune hydrops fetalis and identified 108 fetuses affected with LSDs (6.3 %), 29 of them with mucopolysaccharidosis type VII (MPS VII), and six with GSD IV (0.3 %). In the AF of 873 pregnancies, investigated because of intrauterine growth restriction and/or abnormal genitalia, we diagnosed 32 fetuses affected with Smith-Lemli-Opitz syndrome (3.7 %).

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.