Mitochondrial mutation in adult patient with Hypertrophic Cardiomyopathy and renal failure

Background: Mitochondrial diseases (MDs) (1:5000-10000) represents a wide group of human disorders associated with mitochondrial DNA (mtDNA) variations causing defect of oxidative phosphorylation system, whereas nuclear genome mutations are somewhat rare. The extremely heterogeneous clinical phenotype, extending from oligosymptomatic condition to complex syndromes involving neurological, ophtalmological, gastroenterological and endocrine features, depends to the involved tissue well as to the specific mtDNA mutations and their heteroplasmic level. Diabetes and deafness are common features of mitochondrial diseases, while renal alterations are rarely reported, especially in adults, probably because of lack of association to mitochondrial conventional phenotypes. Case Presentation: We investigated a 62 years old male affected by hypertrophic cardiomyopathy (HCM) and renal failure that caused already a bilateral transplantation. Pathological anamnesis revealed also diabetes, deafness and Crohn disease. Family history of cardiomyopathy showed a strong mitochondrial involvement. The proband's mother, three brothers (one of which died of renal failure at 26 years), the sister and her child were affected. Materials and Methods: Genomic DNA from peripheral blood and buccal cells was extracted with the Kit-Nucleon-BACC2 (Illustra DNA-Extraction Kit-BACC2-GE Healthcare, UK) and the whole mitochondrial genome was amplified by two pair of primers designed in our laboratory to generate two overlapping fragments. The PCR products were then sequenced and compared to mitochondrial reference sequence (rCRS NC_012920). Results and Discussion: In both biological samples the mtDNA analysis showed the heteroplasmic A3243G mutation in the tRNALeu (UUR), frequently associated with MDs. A cardiological involvement leading to hypertrophic remodelling, caused to mitochondria intermyofibrillar proliferation, occurs up to 40% of patients with mtDNA disease. Molecular backgrounds of mitochondrial cardiomyopathy of adult age are still quite poorly known and the A3243G mutation in tRNA Leu(UUR) of mtDNA has been reported in 40-60% of patients with HCM. The interesting finding presented here support the knowledge that mitochondrial gene altertation represents a possible etiology in cardiological patients with unexplained renal failure. This is particularly true, as in this case, when other associated symtoms linked with dysfunctional oxidative phosphorylation are present. The case presented in this report further suggests that a differential diagnosis in presence of HCM should be solved by a multidisciplinary approach together with mutation analysis of mitochondrial DNA

Molecular analysis has allowed the definitive diagnosis of multiple acyl-CoA dehydrogenase deficiency (MADD)

Multiple acyl-CoA dehydrogenation deficiency (MADD) is a rare autosomal recessive disorder due to defects in the electron transfer flavoprotein (ETF) or in the electron transfer flavoprotein dehydrogenase (ETFDH) enzymes, involved in the mitochondrial electron transport chain. Patients with MADD fall into different clinical phenotypes, ranging from a severe neonatal presentation, with metabolic acidosis, cardiomyopathy and liver disease to a mild childhood/adult disease, with episodic metabolic decompensation, muscle weakness and respiratory failure.Nowadays, the MADD diagnosis is established by the presence of dicarboxylic organic acids and acylglycine derivatives in the urine and increased levels of medium-and long-chain acylcarnitines in the blood. Mutations in ETFA, ETFB, ETFDH genes, encoding for alpha and beta subunits of ETF and for ETF-dehydrogenase are associated with MADD. We report the case of a three years old child, affected by lethargy and asthenia associated with anorexia. Biochemical analyses showed hypoketotic hypoglycemia with remarkable increments in transaminases, lactic dehydrogenase, aldolase and creatine kinase. The chromatographic layout of urinary organic acids showed a typical dicarboxylic aciduria. Thus, based on these features, MADD was suspected. Fifteen years later, at the age of 19, MADD diagnosis was confirmed by molecular analysis, showing a compound heterozygosity for the mutations c.1074G>C (p.R358S; HGMD: CM031670 in HGMD database) and c.1073G>A (p.R358K) in the ETFDH gene. The c.1073G>A (p.R358K; rs796051959) mutation is reported in ClinVar database as pathogenic allele, although lacking link to a specific clinical condition. However, familial segregation study and in silico analysis, performed by bioinformatics tools, confirmed that this substitution is likely pathogenetic. Her parents were healthy carriers of one of the two mutations. It is known that the severity of the clinical phenotype of MADD may be related to the type of mutation in the ETFA/ETFB/ETFDH genes. Particularly, missense mutations in the ETFDH gene, leaving a detectable residual enzyme activity, may account for the milder form of the disease, as is the case here. In conclusion we suggest that molecular analysis is essential to the definitive diagnosis of MADD and to direct the adequate therapeutic management. Thus, through a close nutritional follow up, a few months ago the patient gave birth to a healthy boy. References Olsen et al. Clear relationship between ETF/ETFDH genotype and phenotype in patients with multiple acyl-CoA dehydrogenation deficiency. Hum Mutat. 2003; 22:12–23

A new case of Congenital Hyperinsulinemic Hypoglycemia due to M/SCHAD deficiency: the contribution of metabolic and molecular diagnosis for the management

Congenital Hyperinsulinemic Hypoglycemia (CHH) is a rare metabolic disease (prevalence <1/1.000.000) characterized by a persistent hypoglycemia and high secretion of insulin in the neonatal and infancy period. An early management of patients with CHH is mandatory to avoid brain damage. Recent advances in molecular analysis have linked CHH to mutations in nine genes: ABCC8, KCNJ11, GCK causing either diazoxide-responsive or diazoxide-unresponsive Hyperinsulinemic Hypoglycemia, and GLUD1, HADH, SLC16A1, UCP2, HNF4A and HNF1A, causing generally diazoxide-responsive CHH. However, HADH defect is the most common form in presence of consanguinity and diazoxide-responsiveness. The HADH gene codifies the M/SCHAD mitochondrial enzyme, which catalyses the penultimate reaction in the β-oxidation of medium and short-chain fatty acids, causing in some affected individuals an elevated plasmatic hydroxybutyrylcarnitine and urinary medium-chain dicarboxylic, and 3-hydroxydicarboxylic metabolites. To date about 40 cases of M/SCHAD defect have been reported in literature.We report here a new case of CHH due to M/SCHAD deficiency. The index case was a Pakistan infant, born from consanguineous parents, showing a diazoxide-responsive hyperinsulinism and organic aciduria. The M/SCHAD deficiency was confirmed by the molecular diagnosis performed by sequencing of HADH gene, which revealed the presence of the nonsense mutation c.706C>T (p.R236*) in HADH gene, at homozygous state, while both parents were heterozygous for the mutated allele. The patient started diazoxide treatment at the maximum dose of 10 mg/kg/day, which resulted in adverse drug reactions (hypertrichosis, peripheral edemas and persistent hypertension) gradually solved with antihypertensive regimen. Diazoxide was progressively titrated to 2 mg/kg/ day with good results in glycemic control and no hypertensive crisis. Low organic aciduria was followed.In conclusion, when the metabolic profile suggests a CHH disorder, the molecular analysis is necessary for the precise diagnosis and the appropriate counseling to the parents, also for the possibility of a prenatal diagnosis. In this setting, the definitive diagnosis of CHH, due to M/SCHAD deficiency, may suggest also the most appropriate therapeutic intervention to avoid both risk of worsening or adverse drug effect

Clinical and genetic characterization of patients with hypertrophic cardiomyopathy and right atrial enlargement

AIMS: Prevalence and clinical significance of right atrial enlargement (RAE) has been poorly characterized in hypertrophic cardiomyopathy. METHODS: One hundred and sixty consecutive patients with hypertrophic cardiomyopathy (35.5 ± 20 years; 64% men) were studied. They underwent clinical examination, standard ECG, M-mode, 2D and Doppler echocardiography, stress test and ECG Holter monitoring. Major adverse cardiac events were considered: cardiac death (sudden death, heart failure death); cardiac transplant; resuscitated cardiac arrest or appropriate implantable cardioverter defibrillator discharge. Genetic analysis of eight sarcomeric genes was performed using Sanger sequencing. RESULTS: RAE was observed in 22 patients (14%), associated with left atrial enlargement in all cases. Patients with RAE were likely to have restrictive mitral pattern (P < 0.001) and had higher New York Heart Association (P < 0.001), N-terminal prohormone of brain natriuretic peptide (P < 0.001), left atrial volume index (P < 0.001), lateral (P = 0.04) and septal (P = 0.002) E/e', systolic pulmonary artery pressure (P < 0.001) and lower ejection fraction (all P < 0.001). On cardiopulmonary exercise testing, peak VO2 was lower and VE/VCO2 higher in patients with RAE (P < 0.001). During a mean follow-up of 4 ± 2.1 years, 30 major adverse cardiac events in 24 patients (15%) were observed. Cox proportional hazards regression analysis identified RAE as an independent predictor of major adverse cardiac events (odds ratio = 2.6; confidence interval 1.5-4.6; P = 0.001). In patients with RAE who were genetically tested, there was a higher prevalence of sarcomeric gene mutations (68%), double mutations (16%) and troponin T mutations (21%). CONCLUSION: RAE is present in a small subset of patients with hypertrophic cardiomyopathy, and largely reflects increased pulmonary pressures because of severe diastolic and/or systolic left ventricular dysfunction. Patients with RAE had a higher prevalence of sarcomeric gene mutations, troponin T mutations and complex genotypes. In conclusion, RAE may serve as a very useful marker of disease progression and adverse outcome in patients with sarcomeric hypertrophic cardiomyopathy

The hidden fragility in the heart of the athletes: A review of genetic biomarkers

Sudden cardiac death (SCD) is a devastating event which can also affect people in apparent good health, such as young athletes. It is known that intense and continuous exercise along with a genetic background that predisposes a person to the risk of fatal arrhythmias is a trigger for SCD. Therefore, knowledge of the athlete’s genetic conditions underlying the onset of SCD must be extended, in order to develop new effective prevention and/or therapeutic strategies. Arrhythmic features occur across a broad spectrum of cardiac diseases, sometimes presenting with overlapping phenotypes. The genetic basis of arrhythmogenic disorders has been greatly highlighted in the last 30 years, and has shown marked heterogeneity. The advent of next-generation sequencing has constantly updated our understanding of the genetic basis of arrhythmogenic diseases and is laying the foundation for precision medicine. With the exception of a few clinical cases involving a single athlete showing a highly suspected phenotype for the presence of a heart disease, there are few studies to date that analysed the applicability of genetic testing on cohorts of athletes. This evidence shows that genetic testing can contribute to the diagnosis of up to 13% of athletes; however, the presence of clinical markers is essential. This review aims to provide a reference collection on current knowledge of the genetic basis of sudden cardiac death in athletes and to review updated evidence on the effectiveness of genetic testing in early identification of athletes at risk for SCD

Genetic pre-participation screening in selected athletes: a new tool for the prevention of sudden cardiac death?

Sudden cardiac death (SCD) of athletes is a topical issue. “Borderline cardiac abnormalities”, which occur in ~2% of elite male athletes, may result in SCD, which may have a genetic base. Genetic analysis may help identify pathological cardiac abnormalities. We performed phenotype-guided genetic analysis in athletes who, pre-participation, showed ECG and/or echo “borderline” abnormalities, to discriminate subjects at a greater risk of SCD. Methods: We studied 24 elite athletes referred by the National Federation of Olympic sports; and 25 subjects seeking eligibility to practice agonistic sport referred by the Osservatorio Epidemiologico della Medicina dello Sport della Regione Campania. Inclusion criteria: a) ECG repolarization borderline abnormalities; b) benign ventricular arrhythmias; c) left ventricular wall thickness in the grey zone of physiology versus pathology (max wall thickness 12-15 mm in females; 13-16 mm in males). Based on the suspected phenotype, we screened subjects for the LMNA gene, for 8 sarcomeric genes, 5 desmosomal genes, and cardiac calcium, sodium and potassium channel disease genes. Results: Genetic analysis was completed in 37/49 athletes, 22 competitive and 27 non-competitive athletes, showing “borderline” clinical markers suggestive of hypertrophic cardiomyopathy (HCM,n. 24), dilated cardiomyopathy (n. 4), arrhythmogenic right ventricular dysplasia/cathecholaminergic polymorphic ventricular tachycardia (ARVD/CPVT, n. 11), long QT syndrome (LQTS, n. 4), sick sinus syndrome (SSS, n. 5), Brugada syndrome (BrS, n. 1). We identifyed 11 mutations in 9 athletes (an ARVD athlete was compound heterozygote for the PKP2 gene and an HCM athlete was double heterozygote for the MYBPC3 and TNNT2 genes): 3 known mutations related to LQTS, HCM and ARVD, respectively, and 8 novel mutations, located in the SCN5A, RyR2, PKP2, MYBPC3 and ACTC1 genes. The new mutations were absent in ~800 normal chromosomes and were predicted “probably damaging” by in silico analysis. Patch clamp analysis in channelopathies indicated for some mutation abnormal biophysical behavior of the corresponding mutant protein. Conclusion: Genetic analysis may help distinguish between physiology and pathology in athletes with clinically suspected heart disease

Physical activity and thrombophilic risk in a short series

The role of influence on protein C anticoagulant system and PC deficiency-related thrombophilic risk due to strenuous physical exercise is still under discussion. To investigate the modification of the protein C anticoagulant pathway after vigorous exercise, we measured ProC® Global assay, a protein C activity dependent clotting time, in 20 healthy subjects before and immediately after maximal treadmill exercise, and at 5, 15, 30 and 60 min in the recovery phase. The most evident change was a shortening of ProC® Global clotting time from the average basal value of 123 sec to 84 sec at 30 min in post-exercise. Our study shows that the coagulation unbalance observed after strenuous exercise and with no consequence in healthy individuals with normal PC level, could increase the thrombophilic risk in silent carriers of significant defects of the protein C system and occasionally trigger an episode of deep vein thrombosis

Prevalence and clinical significance of red flags in patients with hypertrophic cardiomyopathy

Introduction: We sought to determine prevalence and predictive accuracy of clinical markers (red flags, RF), known to be associated with specific systemic disease in a consecutive cohort of patients with hypertrophic cardiomyopathy (HCM). / Methods: We studied 129 consecutive patients (23.7 ± 20.9 years, range 0–74 years; male/female 68%/32%). Pre-specified RF were categorized into five domains: family history; signs/symptoms; electrocardiography; imaging; and laboratory. Sensitivity (Se), specificity (Sp), negative predictive value (NPV), positive predictive value (PPV), and predictive accuracy of RF were analyzed in the genotyped population. / Results: In the overall cohort of 129 patients, 169 RF were identified in 62 patients (48%). Prevalence of RF was higher in infants (78%) and in adults >55 years old (58%). Following targeted genetic and clinical evaluation, 94 patients (74%) had a definite diagnosis (sarcomeric HCM or specific causes of HCM). We observed 14 RF in 13 patients (21%) with sarcomeric gene disease, 129 RF in 34 patients (97%) with other specific causes of HCM, and 26 RF in 15 patients (45%) with idiopathic HCM (p  55yo. Se, Sp, PPV, NPV and PA of RF were 97%, 70%, 55%, 98% and 77%, respectively. Single and clinical combination of RF (clusters) had an high specificity, NPV and predictive accuracy for the specific etiologies (syndromes/metabolic/infiltrative disorders associated with HCM). / Conclusions: An extensive diagnostic work up, focused on analysis of specific diagnostic RF in patients with unexplained LVH facilitates a clinical diagnosis in 74% of patients with HCM