The genetic landscape of mitochondrial diseases in the next-generation sequencing era: a Portuguese cohort study.

Introduction: Rare disorders that are genetically and clinically heterogeneous, such as mitochondrial diseases (MDs), have a challenging diagnosis. Nuclear genes codify most proteins involved in mitochondrial biogenesis, despite all mitochondria having their own DNA. The development of next-generation sequencing (NGS) technologies has revolutionized the understanding of many genes involved in the pathogenesis of MDs. In this new genetic era, using the NGS approach, we aimed to identify the genetic etiology for a suspected MD in a cohort of 450 Portuguese patients. Methods: We examined 450 patients using a combined NGS strategy, starting with the analysis of a targeted mitochondrial panel of 213 nuclear genes, and then proceeding to analyze the whole mitochondrial DNA. Results and Discussion: In this study, we identified disease-related variants in 134 (30%) analyzed patients, 88 with nuclear DNA (nDNA) and 46 with mitochondrial DNA (mtDNA) variants, most of them being pediatric patients (66%), of which 77% were identified in nDNA and 23% in mtDNA. The molecular analysis of this cohort revealed 72 already described pathogenic and 20 novel, probably pathogenic, variants, as well as 62 variants of unknown significance. For this cohort of patients with suspected MDs, the use of a customized gene panel provided a molecular diagnosis in a timely and cost-effective manner. Patients who cannot be diagnosed after this initial approach will be further selected for whole-exome sequencing. Conclusion: As a national laboratory for the study and research of MDs, we demonstrated the power of NGS to achieve a molecular etiology, expanding the mutational spectrum and proposing accurate genetic counseling in this group of heterogeneous diseases without therapeutic options.

The natural history of classic galactosemia: lessons from the GalNet registry.

BACKGROUND: Classic galactosemia is a rare inborn error of carbohydrate metabolism, caused by a severe deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT). A galactose-restricted diet has proven to be very effective to treat the neonatal life-threatening manifestations and has been the cornerstone of treatment for this severe disease. However, burdensome complications occur despite a lifelong diet. For rare diseases, a patient disease specific registry is fundamental to monitor the lifespan pathology and to evaluate the safety and efficacy of potential therapies. In 2014, the international Galactosemias Network (GalNet) developed a web-based patient registry for this disease, the GalNet Registry. The aim was to delineate the natural history of classic galactosemia based on a large dataset of patients. METHODS: Observational data derived from 15 countries and 32 centers including 509 patients were acquired between December 2014 and July 2018. RESULTS: Most affected patients experienced neonatal manifestations (79.8%) and despite following a diet developed brain impairments (85.0%), primary ovarian insufficiency (79.7%) and a diminished bone mineral density (26.5%). Newborn screening, age at onset of dietary treatment, strictness of the galactose-restricted diet, p.Gln188Arg mutation and GALT enzyme activity influenced the clinical picture. Detection by newborn screening and commencement of diet in the first week of life were associated with a more favorable outcome. A homozygous p.Gln188Arg mutation, GALT enzyme activity of ≤ 1% and strict galactose restriction were associated with a less favorable outcome. CONCLUSION: This study describes the natural history of classic galactosemia based on the hitherto largest data set.

Liver involvement in congenital disorders of glycosylation (CDG). A systematic review of the literature.

Congenital disorders of glycosylation (CDG) are a rapidly growing family of genetic diseases caused by defects in glycosylation. Nearly 100 CDG types are known so far. Patients present a great phenotypic diversity ranging from poly- to mono-organ/system involvement and from very mild to extremely severe presentation. In this literature review, we summarize the liver involvement reported in CDG patients. Although liver involvement is present in only a minority of the reported CDG types (22 %), it can be debilitating or even life-threatening. Sixteen of the patients we collated here developed cirrhosis, 10 had liver failure. We distinguish two main groups: on the one hand, the CDG types with predominant or isolated liver involvement including MPI-CDG, TMEM199-CDG, CCDC115-CDG, and ATP6AP1-CDG, and on the other hand, the CDG types associated with liver disease but not as a striking, unique or predominant feature, including PMM2-CDG, ALG1-CDG, ALG3-CDG, ALG6-CDG, ALG8-CDG, ALG9-CDG, PGM1-CDG, and COG-CDG. This review aims to facilitate CDG patient identification and to understand CDG liver involvement, hopefully leading to earlier diagnosis, and better management and treatment.

[Simultaneous occurrence of neurofibromatosis and tuberous sclerosis, acquired as neo-mutations]. / Ocurrencia simultánea de neurofibromatosis y esclerosis tuberosa, adquiridas como neomutaciones.

INTRODUCTION: Neurofibromatosis type 1 and tuberous sclerosis are two distinct neurocutaneous syndromes that result of a mutation of tumoral suppressor genes, increasing the risk of tumorigenesis. They both have dominant autosomal hereditariness with half of the cases corresponding to new mutations. They are situations rarely associated. CASE REPORT: A boy without any family history of neurocutaneous disorders who had characteristics of both neurofibromatosis and tuberous sclerosis, as cafe-au-lait patches, six greater than 0.5 cm, macrocephaly, optic nerve glioma, focal alterations of the myelin vacuolization of the white matter from both cerebellar hemispheres, brain stem, basal ganglia, characteristic of type 1 neurofibromatosis. He also presented hypopigmentation spots, infantile spasms, and imagiologic findings of cortical areas with altered mielinization on the white matter, left talamo-caudado sulcus calcifications, cortical tubers, Taylor cortical dysplasia, subependimary nodes, characteristically of tuberous sclerosis. The child also had psycho motor development delay. CONCLUSION: The diagnosis of both disorders was confirmed by genetic study. Parents study was negative, so we can confirm the simultaneous occurrence of two new mutations which is unusually rare.

Ocurrencia simultánea de neurofibromatosis y esclerosis tuberosa, adquiridas como neomutaciones / Simultaneous occurrence of neurofibromatosis and tuberous sclerosis, acquired as neo-mutations

La neurofibromatosis tipo 1 y la esclerosis tuberosa son dos síndromes neurocutáneos distintos, resultadode la mutación de genes supresores tumorales, que aumentan la propensión a la génesis tumoral. Ambas tienen una herencia autosómica dominante y la mitad de los casos corresponden a nuevas mutaciones. Estas enfermedades raramente se presentan asociadas. Caso clínico. Niño sin antecedentes familiares de enfermedades neurocutáneas, que presenta característicasde neurofibromatosis y de esclerosis tuberosa, principalmente manchas ‘café con leche’ (seis de ellas con un diámetro superior a 0,5 cm), macrocefalia, glioma del nervio óptico y alteraciones focales de vacuolización de la mielina en la sustanciablanca de los hemisferios cerebelosos, tronco cerebral y ganglios de la base, características de la neurofibromatosis tipo 1. Por otro lado, presenta manchas hipopigmentadas, espasmos infantiles y evaluación imaginológica de las áreas de alteraciónde la mielinización de la corteza para la sustancia blanca, calcificaciones en el surco talamocaudado a la izquierda, tuberosidades corticales, displasia cortical focal de Taylor y múltiples nódulos subependimarios, características que son compatibles con la esclerosis tuberosa. El niño también presenta retraso en el desarrollo psicomotor. Conclusión. El diagnósticode ambas enfermedades se confirmó gracias al estudio genético. La evaluación de los progenitores fue negativa, por lo que se puede confirmar la presencia de dos neomutaciones concomitantes, un hecho que es excepcionalmente raro

Neurofibromatosis type 1 and tuberous sclerosis are two distinct neurocutaneous syndromes thatresult of a mutation of tumoral suppressor genes, increasing the risk of tumorogenese. They both have dominant autosomal hereditariness with half of the cases corresponding to new mutations. They are situations rarely associated. Case report. A boy without any family history of neurocutaneous disorders who had characteristics of both neurofibromatosis and tuberoussclerosis, as café-au-lait patches, six greater than 0.5 cm, macrocephaly, optic nerve glioma, focal alterations of the myelin vacuolization of the white matter from both cerebellar hemispheres, brain stem, basal ganglia, characteristic of type 1 neurofibromatosis. He also presented hypopigmentation spots, infantile spasms, and imagiologic findings of cortical areaswith altered mielinization on the white matter, left talamo-caudado sulcus calcifications, cortical tubers, Taylor cortical dysplasia, subependimary nodes, characteristically of tuberous sclerosis. The child also had psycho motor development delay.Conclusion. The diagnosis of both disorders was confirmed by genetic study. Parents study was negative, so we can confirm the simultaneous occurrence of two new mutations which is unusually rare