Clinical, Genetic, and Histological Characterization of Patients with Rare Neuromuscular and Mitochondrial Diseases Presenting with Different Cardiomyopathy Phenotypes

Cardiomyopathies are mostly determined by genetic mutations affecting either cardiac muscle cell structure or function. Nevertheless, cardiomyopathies may also be part of complex clinical phenotypes in the spectrum of neuromuscular (NMD) or mitochondrial diseases (MD). The aim of this study is to describe the clinical, molecular, and histological characteristics of a consecutive cohort of patients with cardiomyopathy associated with NMDs or MDs referred to a tertiary cardiomyopathy clinic. Consecutive patients with a definitive diagnosis of NMDs and MDs presenting with a cardiomyopathy phenotype were described. Seven patients were identified: two patients with ACAD9 deficiency (Patient 1 carried the c.1240C>T (p.Arg414Cys) homozygous variant in ACAD9; Patient 2 carried the c.1240C>T (p.Arg414Cys) and the c.1646G>A (p.Ar549Gln) variants in ACAD9); two patients with MYH7-related myopathy (Patient 3 carried the c.1325G>A (p.Arg442His) variant in MYH7; Patient 4 carried the c.1357C>T (p.Arg453Cys) variant in MYH7); one patient with desminopathy (Patient 5 carried the c.46C>T (p.Arg16Cys) variant in DES); two patients with mitochondrial myopathy (Patient 6 carried the m.3243A>G variant in MT-TL1; Patient 7 carried the c.253G>A (p.Gly85Arg) and the c.1055C>T (p.Thr352Met) variants in MTO1). All patients underwent a comprehensive cardiovascular and neuromuscular evaluation, including muscle biopsy and genetic testing. This study described the clinical phenotype of rare NMDs and MDs presenting as cardiomyopathies. A multidisciplinary evaluation, combined with genetic testing, plays a main role in the diagnosis of these rare diseases, and provides information about clinical expectations, and guides management.

Contribution of Genetic Test to Early Diagnosis of Methylenetetrahydrofolate Reductase (MTHFR) Deficiency: The Experience of a Reference Center in Southern Italy

BACKGROUND

the deficiency of 5,10-Methylenetetrahydrofolate reductase (MTHFR) constitutes a rare and severe metabolic disease and is included in most expanded newborn screening (NBS) programs worldwide. Patients with severe MTHFR deficiency develop neurological disorders and premature vascular disease. Timely diagnosis through NBS allows early treatment, resulting in improved outcomes.

METHODS

we report the diagnostic yield of genetic testing for MTHFR deficiency diagnosis, in a reference Centre of Southern Italy between 2017 and 2022. MTHFR deficiency was suspected in four newborns showing hypomethioninemia and hyperhomocysteinemia; otherwise, one patient born in pre-screening era showed clinical symptoms and laboratory signs that prompted to perform genetic testing for MTHFR deficiency.

RESULTS

molecular analysis of the MTHFR gene revealed a genotype compatible with MTHFR deficiency in two NBS-positive newborns and in the symptomatic patient. This allowed for promptly beginning the adequate metabolic therapy.

CONCLUSIONS

our results strongly support the need for genetic testing to quickly support the definitive diagnosis of MTHFR deficiency and start therapy. Furthermore, our study extends knowledge of the molecular epidemiology of MTHFR deficiency by identifying a novel mutation in the MTHFR gene.

Long-term monitoring for short/branched-chain acyl-CoA dehydrogenase deficiency: A single-center 4-year experience and open issues

INTRODUCTION

Short/branched-chain acyl-CoA dehydrogenase deficiency (SBCADD) is an inherited disorder of L-isoleucine metabolism due to mutations in the ACADSB gene. The role of current diagnostic biomarkers [i.e., blood 2-methylbutyrylcarnitine (C5) and urine 2-methylbutyrylglycine (2MBG)] in patient monitoring and the effects of proposed treatments remain uncertain as follow-data are lacking. This study presents first systematic longitudinal biochemical assessment in SBCADD patients.

METHODS

A retrospective, observational single-center study was conducted on newborns born between 2017 and 2020 and suspected with SBCADD. Biochemical, molecular, clinical and dietary data collected upon NBS recall and during the subsequent follow-up were recorded.

RESULTS

All enrolled subjects (n = 10) received adequate protein intake and L-carnitine supplementation. Nine subjects were diagnosed with SBCADD. During the follow-up [median: 20.5 (4-40) months] no patient developed symptoms related to SBCADD. No patient normalized serum C5 and urine 2MBG values. In 7/9 SBCADD patients mean serum C5 values decreased or stabilized compared to their first serum C5 value. A major increase in serum C5 values was observed in two patients after L-carnitine discontinuation and during intercurrent illness, respectively. Urine 2MBG values showed moderate intra-patient variability.

DISCUSSION

The relatively stable serum C5 values observed during L-carnitine supplementation together with C5 increase occurring upon L-carnitine discontinuation/intercurrent illness may support the value of serum C5 as a monitoring biomarker and the benefit of this treatment in SBCADD patients. The role of urine 2MBG in patient monitoring remains uncertain. As all patients were asymptomatic, no association between biochemical parameters and clinical phenotype could be investigated in this study.

NGS Gene Panel Analysis Revealed Novel Mutations in Patients with Rare Congenital Diarrheal Disorders

Congenital diarrheal disorders (CDDs) are early-onset enteropathies generally inherited as autosomal recessive traits. Most patients with CDDs require rapid diagnosis as they need immediate and specific therapy to avoid a poor prognosis, but their clinical picture is often overlapping with a myriad of nongenetic diarrheal diseases. We developed a next-generation sequencing (NGS) panel for the analysis of 92 CDD-related genes, by which we analyzed patients suspect for CDD, among which were (i) three patients with sucrose-isomaltase deficiency; (ii) four patients with microvillous inclusion disease; (iii) five patients with congenital tufting enteropathy; (iv) eight patients with glucose-galactose malabsorption; (v) five patients with congenital chloride diarrhea. In all cases, we identified the mutations in the disease-gene, among which were several novel mutations for which we defined pathogenicity using a combination of bioinformatic tools. Although CDDs are rare, all together, they have an incidence of about 1%. Considering that the clinical picture of these disorders is often confusing, a CDD-related multigene NGS panel contributes to unequivocal and rapid diagnosis, which also reduces the need for invasive procedures.

Prenatal Diagnosis of Cystic Fibrosis and Hemophilia: Incidental Findings and Weak Points

Because of the progression of genetics and genomics, the demand for prenatal diagnosis (PD) for inherited genetic diseases has increased. However, several incidental findings may emerge during PD, like misattributed paternity, the evidence of disease in a parent, and the possible misinterpretation of the results because of complex alleles or de novo mutations that have several implications. In a retrospective observational study on all the couples referred to our Medical School (1993–2018) for PD of genetic inherited diseases (n = 1502), we selected the cases of PD for cystic fibrosis (CF, n = 239) and hemophilia A and B (HA, HB, n = 47), revising all incidental findings previously mentioned. We found one case in which a technical error led to PD of carrier in two siblings that were born affected by CF, four cases of misattributed paternity, eight cases of asymptomatic parents revealed as affected by CF transmembrane regulator (CFTR)-related disorders, a case of a novel complex allele that could have caused the diagnosis of CF in a carrier fetus, and a case of a de novo mutation in a mother (already a carrier) that caused hemophilia in a child that PD had revealed as healthy. We present these conditions as clinical cases and discuss the technical, clinical, ethical, and legal aspects to be considered.

First trimester ultrasound features of X-linked Opitz syndrome and early molecular diagnosis: case report and review of the literature

X-linked Opitz G/BBB syndrome (XLOS) is a multiple congenital disorder inherited in an X-linked manner. XLOS may be suspected, in prenatal age, on the basis of sonographic findings in the second and/or third trimester of gestation. Pathogenetic variants in MID1 gene have been reported in individuals with XLOS. Prenatal genetic testing is offered for pregnancies at risk, in which the mutation in the family has been identified. To date no cases of prenatal diagnosis, based on first-trimester ultrasound data, have been reported. We present a case of a fetus at 12 gestational weeks with ultrasound multiple anomalies, including increased nuchal translucency, heart defects, cleft lip and palate, enlarged fourth ventricle absence of ductus venosus and family hystory of XLOS. The genetic prenatal test detected the c(0).1286-1G > T mutation of MID1 gene. Data about prenatal ultrasonographic findings consistent with XLOS are limited to second and third trimester. This is the first case reporting ultrasound detectable midline defects suggestive of XLOS as early as the first trimester of gestation. This case also suggests that when multiple anomalies are detected in a fetus with normal chromosomal structure, the possibility of a monogenic disorder must be considered.

Two cases of microvillous inclusion disease caused by novel mutations in MYO5B gene

Microvillous inclusion disease (MVID) typically appears with severe chronic diarrhea in the few days after birth and rapidly causes dehydration and metabolic acidosis. In this context, presenting two novel cases, we underline the crucial importance of mutation analysis for the diagnosis of this disease that may be easily misdiagnosed.

Case Study: Cystic Fibrosis in the Newborn

Cystic fibrosis (CF) is considered one of the most commonly occurring fatal genetic disorders. This disorder is associated with pancreatic insufficiency and pulmonary complications. However, at birth the initial complications are associated with bowel obstruction. Cystic fibrosis management warrants an interdisciplinary team because this disorder affects various organ systems. Effective management of the newborn with CF assists in improving the child's overall prognosis. Family support is critical throughout the prenatal and postnatal periods. The case presented reviews a child born with suspected CF and the clinical course within the NICU.

An "ex vivo model" contributing to the diagnosis and evaluation of new drugs in cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene. About 2000 mutations have been described so far. We setup an ex vivo model of human nasal epithelial cells (HNECs) to study CF patients testing the effect of novel mutations and molecular therapies. We performed sampling (by brushing), followed by culture and analysis of HNECs using a series of molecular techniques. We performed 50 brushings from CF patients and controls. Using cultured cells, we: i) demonstrated the widely heterogeneous CFTR expression in patients and in controls; ii) defined the splicing effect of a CFTR mutation; iii) assessed the CFTR gating activity in patients bearing different mutations; iv) demonstrated that butyrate significantly enhances CFTR expression. Based on our data, we can conclude: 1) HNEC brushing is performed without anaesthesia and is well tolerated in all CF patients (children and adults); 2) HNECs can be preserved for up to 48 hours before culture allowings multicentre studies; 3) HNECs culture can be considered a suitable model to study the molecular effects of new CFTR gene mutations and/or uncertain meaning specific mutations of carriers; 4) an ex vivo model of HNECs may be used to evaluate, before human use, the effect of new drugs on patients’ cells bearing specific CFTR mutations; 5) the methodology is adequate for a quantitative measurement, by fluorescence, of the CFTR gating activity of the HNECs from patients with different genotypes identifying: a) CF patients bearing two severe mutations with an activity < 10% (compared to controls – 100%); b) CF patients bearing at least a mild mutation with an activity of 10-20%; c) CF carriers (heterozygous subjects) with an activity between 40-70%.

The SEeMORE strategy: single-tube electrophoresis analysis-based genotyping to detect monogenic diseases rapidly and effectively from conception until birth

BACKGROUND

The development of technologies that detect monogenic diseases in embryonic and fetal samples are opening novel diagnostic possibilities for preimplantation genetic diagnosis (PGD) and prenatal diagnosis (PND) thereby changing laboratory practice. Molecular diagnostic laboratories use different workflows for PND depending on the disease, type of biological sample, the presence of one or more known mutations, and the availability of the proband. Paternity verification and contamination analysis are also performed. The aim of this study was to test the efficacy of a single workflow designed to optimize the molecular diagnosis of monogenic disease in families at-risk of transmitting a genetic alteration.

METHODS

We used this strategy, which we designated "SEeMORE strategy" (Single-tube Electrophoresis analysis-based genotyping to detect MOnogenic diseases Rapidly and Effectively from conception to birth). It consists of a multiplex PCR that simultaneously carries out linkage analysis, direct analysis, maternal contamination and parenthood testing. We analyzed samples from previously diagnosed families for PND (cystic fibrosis or Duchenne muscular dystrophy) without, however, knowing the results.

RESULTS

The results obtained with the SEeMORE strategy concurred with those obtained with traditional PND. In addition, this strategy has several advantages: (i) use of one or a few cells; (ii) reduction of the procedure to 1 day; and (iii) a reduction of at least 2-3-fold of the analytic cost.

CONCLUSIONS

The SEeMORE strategy is effective for the molecular diagnosis of monogenic diseases, irrespective of the amount of starting material and of the disease mutation, and can be used for PND and PGD.

A rare case of sterol-C4-methyl oxidase deficiency in a young Italian male: Biochemical and molecular characterization

Inborn defects of cholesterol biosynthesis are metabolic disorders presenting with multi-organ and tissue anomalies. An autosomal recessive defect involving the demethylating enzyme C4-methyl sterol (SC4MOL) has been reported in only 4 patients so far. In infancy, all patients were affected by microcephaly, bilateral congenital cataracts, growth delay, psoriasiform dermatitis, immune dysfunction, and intellectual disability. Herein, we describe a new case of SC4MOL deficiency in which a 19-year-old Italian male was affected by bilateral congenital cataracts, growth delay and learning disabilities, behavioral disorders and small stature, but not microcephaly. Our patient had abundant scalp dandruff, without other skin manifestations. Analysis of the blood sterol profile showed accumulation of C4-monomethyl and C4-dimethyl sterols suggesting a deficiency of the SC4MOL enzyme. Sequencing of the MSMO1 gene (also known as the "SC4MOL" gene) confirmed mutations in each allele (c.731A>G, p.Y244C, which is already known, and c.605G>A, p.G202E, which is a novel variant). His father carried c.731A>G mutation, whereas his mother carried c.605G>A. Thus, the combination of multiple skills and methodologies, in particular, blood sterol profiling and genetic analysis, led to the diagnosis of a new case of a very rare defect of cholesterol biosynthesis. Consequently, we suggest that these two analyses should be performed as soon as possible in all undiagnosed patients affected by bilateral cataracts and developmental delay.

Twelve Novel Mutations in the SLC26A3 Gene in 17 Sporadic Cases of Congenital Chloride Diarrhea

OBJECTIVES

We aimed to improve the knowledge of pathogenic mutations in sporadic cases of congenital chloride diarrhea (CCD) and emphasize the importance of functional studies to define the effect of novel mutations.

METHODS

All member 3 of solute carrier family 26 (SLC26A3) coding regions were sequenced in 17 sporadic patients with CCD. Moreover, the minigene system was used to analyze the effect of 2 novel splicing mutations.

RESULTS

We defined the SLC26A3 genotype of all 17 patients with CCD and identified 12 novel mutations. Using the minigene system, we confirmed the in silico prediction of a complete disruption of splicing pattern caused by 2 of these novel mutations: the c.971+3_971+4delAA and c.735+4_c.735+7delAGTA. Moreover, several prediction tools and a structure-function prediction defined the pathogenic role of 6 novel missense mutations.

CONCLUSIONS

We confirm the molecular heterogeneity of sporadic CCD adding 12 novel mutations to the list of known pathogenic mutations. Moreover, we underline the importance, for laboratories that offer molecular diagnosis and genetic counseling, to perform fast functional analysis of novel mutations.

Points to Consider: Ethical, Legal, and Psychosocial Implications of Genetic Testing in Children and Adolescents

In 1995, the American Society of Human Genetics (ASHG) and American College of Medical Genetics and Genomics (ACMG) jointly published a statement on genetic testing in children and adolescents. In the past 20 years, much has changed in the field of genetics, including the development of powerful new technologies, new data from genetic research on children and adolescents, and substantial clinical experience. This statement represents current opinion by the ASHG on the ethical, legal, and social issues concerning genetic testing in children. These recommendations are relevant to families, clinicians, and investigators. After a brief review of the 1995 statement and major changes in genetic technologies in recent years, this statement offers points to consider on a broad range of test technologies and their applications in clinical medicine and research. Recommendations are also made for record and communication issues in this domain and for professional education.

Congenital diarrhoeal disorders: advances in this evolving web of inherited enteropathies

Congenital diarrhoeal disorders (CDDs) represent an evolving web of rare chronic enteropathies, with a typical onset early in life. In many of these conditions, severe chronic diarrhoea represents the primary clinical manifestation, whereas in others diarrhoea is only a component of a more complex multi-organ or systemic disorder. Typically, within the first days of life, diarrhoea leads to a life-threatening condition highlighted by severe dehydration and serum electrolyte abnormalities. Thus, in the vast majority of cases appropriate therapy must be started immediately to prevent dehydration and long-term, sometimes severe, complications. The number of well-characterized disorders attributed to CDDs has gradually increased over the past several years, and many new genes have been identified and functionally related to CDDs, opening new diagnostic and therapeutic perspectives. Molecular analysis has changed the diagnostic scenario in CDDs, and led to a reduction in invasive and expensive procedures. Major advances have been made in terms of pathogenesis, enabling a better understanding not only of these rare conditions but also of more common diseases mechanisms.

Prenatal molecular diagnosis of inherited neuromuscular diseases: Duchenne/Becker muscular dystrophy, myotonic dystrophy type 1 and spinal muscular atrophy

BACKGROUND

Neuromuscular disease is a broad term that encompasses many diseases that either directly, via an intrinsic muscle disorder, or indirectly, via a nerve disorder, impairs muscle function. Here we report the experience of our group in the counselling and molecular prenatal diagnosis of three inherited neuromuscular diseases, i.e., Duchenne/Becker muscular dystrophy (DMD/BMD), myotonic dystrophy type 1 (DM1), spinal muscular atrophy (SMA).

METHODS

We performed a total of 83 DMD/BMD, 15 DM1 and 54 SMA prenatal diagnoses using a combination of technologies for either direct or linkage diagnosis.

RESULTS

We identified 16, 5 and 10 affected foetuses, respectively. The improvement of analytical procedures in recent years has increased the mutation detection rate and reduced the analytical time.

CONCLUSIONS

Due to the complexity of the experimental procedures and the high, specific professional expertise required for both laboratory activities and the related counselling, these types of analyses should be preferentially performed in reference molecular diagnostic centres.

Prenatal diagnosis of cystic fibrosis: an experience of 181 cases

BACKGROUND

The demand for prenatal diagnosis (PD) of cystic fibrosis (CF) is increasing.

METHODS

We performed pre-test multidisciplinary counselling for 192 couples at CF reproductive risk. In 11/192 (5.7%) cases PD was not performed mainly because counselling revealed a reproductive risk for atypical (mild) CF, while 181 PDs were performed in couples revealed at high risk for CF mainly because they already had a CF child (148/181, 81.8%) or had been identified through cascade screening (28/181, 15.5%).

RESULTS

In 167/181 (92.3%) cases (including two dichorionic twin pregnancies), PD was performed on chorionic villi, and in 14 on amniocyte DNA. Only 1/181 PD was unsuccessful. In all other cases, single tandem repeat analysis excluded maternal contamination, and PD was made within 7 days of sampling. In total 116/180 (64.4%) PDs were made with dot-blot analysis; 40 (22.2%) required gene sequencing; in 4/180 cases we tested the gene for large rearrangements; in 23/180 (12.8%) cases linkage analysis was necessary because parental mutation(s) were unknown. Forty-two out of 180 (23.3%) PDs revealed an affected foetus. All couples but one interrupted pregnancy. The first twin PD revealed the absence (1 foetus) and the presence of one mutation (the other foetus); the second twin PD revealed one parental mutation (1 foetus) and both parental mutations (the other foetus); the couple planned selective interruption.

CONCLUSIONS

PD for CF should be performed in reference laboratories equipped for gene scanning and linkage analysis, with a multidisciplinary staff able to offer counselling to couples during all phases of PD.

Genetic diseases that predispose to early liver cirrhosis

Inherited liver diseases are a group of metabolic and genetic defects that typically cause early chronic liver involvement. Most are due to a defect of an enzyme/transport protein that alters a metabolic pathway and exerts a pathogenic role mainly in the liver. The prevalence is variable, but most are rare pathologies. We review the pathophysiology of such diseases and the diagnostic contribution of laboratory tests, focusing on the role of molecular genetics. In fact, thanks to recent advances in genetics, molecular analysis permits early and specific diagnosis for most disorders and helps to reduce the invasive approach of liver biopsy.

Prenatal diagnosis of haemoglobinopathies: our experience of 523 cases

BACKGROUND

We performed counselling for prenatal diagnosis (PD) of haemoglobinopathies in 372 couples. Thirty-four out of 372 (9.1%) did not undergo PD: six due to spontaneous abortion; nine because it was too difficult to make a decision if PD was positive; 18 because counselling excluded the carrier status of one or both parents; and one because parental mutations were mild.

METHODS

Eleven out of 338 (3.3%) couples underwent PD because they had a thalassaemic child; 106 (31.4%) were found to be at high risk during pre-conceptional screening; 221 (65.4%) because of familiarity. Of 523 PDs in 486 (92.9%), including six dichorionic twin pregnancies, PD was performed on DNA from chorionic villi (CV), and in 37 from amniocytes (7.1%). In 1/523 cases, PD was not completed because DNA from CV was not sufficient; in two cases single tandem repeat analysis revealed maternal contamination of foetal DNA; in 7/522 (1.3%) cases PD revealed non-paternity. In 435/522 (83.3%) cases, PD was performed using reverse dot-blot and ARMS; 34/522 (6.5%) required sequencing. In 53/522 (10.2%) cases it was necessary to test globin loci for large rearrangements.

RESULTS

One hundred and twenty out of 522 (23.0%) PDs revealed an affected foetus. In all but two cases the couple interrupted pregnancy. In the six twin pregnancies PD revealed a normal and a carrier foetus (two cases), carrier status in both foetuses (two cases) and a carrier and an affected foetus (two cases). In these latter cases the couple planned selective interruption.

CONCLUSIONS

Our PD procedure is successful and reliable, and is useful in high-risk areas characterised by molecular heterogeneity.