Facilitations and Hurdles of Genetic Testing in Neuromuscular Disorders

Abstract

Neuromuscular disorders (NMDs) comprise a heterogeneous group of disorders that affect about one in every thousand individuals worldwide. The vast majority of NMDs has a genetic cause, with about 600 genes already identified. Application of genetic testing in NMDs can be useful for several reasons: correct diagnostic definition of a proband, extensive familial counselling to identify subjects at risk, and prenatal diagnosis to prevent the recurrence of the disease; furthermore, identification of specific genetic mutations still remains mandatory in some cases for clinical trial enrollment where new gene therapies are now approaching. Even though genetic analysis is catching on in the neuromuscular field, pitfalls and hurdles still remain and they should be taken into account by clinicians, as for example the use of next generation sequencing (NGS) where many single nucleotide variants of “unknown significance” can emerge, complicating the correct interpretation of genotype-phenotype relationship. Finally, when all efforts in terms of molecular analysis have been carried on, a portion of patients affected by NMDs still remain “not genetically defined”. In the present review we analyze the evolution of genetic techniques, from Sanger sequencing to NGS, and we discuss “facilitations and hurdles” of genetic testing which must always be balanced by clinicians, in order to ensure a correct diagnostic definition, but taking always into account the benefit that the patient could obtain especially in terms of “therapeutic offer”.

An integrated approach to the evaluation of patients with asymptomatic or minimally symptomatic hyperCKemia

“…37,38 Moreover, it must be noted that gene panels must be periodically updated due to the frequent identification of novel causative genes. 39 In our analysis, the most frequent pathogenic variants were in the ANO5 gene, which were identified in eight patients. This finding is in line with those in previous reports, according to which ANO5-related muscle diseases frequently manifest in patients with a long-standing history of hyperCKemia without muscle weakness and commonly present in association with exercise intolerance, myalgia, and, more rarely, episodes of rhabdomyolysis, 40,41 in addition to the muscle biopsy not showing specific pathological signs.…”

“…An important limitation is that the DMD gene was not included in our target gene panel, potentially missing rare DMD point mutations causing isolated hyperCKemia 37,38 . Moreover, it must be noted that gene panels must be periodically updated due to the frequent identification of novel causative genes 39 …”

“… 37 , 38 Moreover, it must be noted that gene panels must be periodically updated due to the frequent identification of novel causative genes. 39 …”

Analyzing Modern Biomolecules: The Revolution of Nucleic-Acid Sequencing – Review

“…In this manner, new sequencing technologies are allowing researchers to better diagnose and analyze diseases [29]. Amongst the many examples available are the fight against complex diseases such as cancer [13,30] and neuromuscular disorders (NMD), involving more than 600 genes, affecting one in every thousand persons worldwide [31], and structural variations (SV), as shown for conditions such as autism. Interestingly, some of them are related to non-coding sequences [32].…”

Genetic Testing for Rare Diseases

“…Barp et al [16] conducted a review about the complexity of the molecular diagnosis of neuromuscular disorders, including gene panels sequencing, whole-exome sequencing, and whole-genome sequencing. They highlight the importance of clinical diagnoses in order to target the appropriate technique and candidate genes according to the suspected clinical entity and the challenge that supposes the pathogenic nature of a high number of variants of unknown significance that are found with the use of next-generation sequencing.…”