Spinal muscular atrophy with respiratory distress type 1 (SMARD1) Report of a Spanish case with extended clinicopathological follow-up

Exploring the relationship between IGHMBP2 gene mutations and spinal muscular atrophy with respiratory distress type 1 and Charcot-Marie-Tooth disease type 2S: a systematic review

Background

IGHMBP2 is a crucial gene for the development and maintenance of the nervous system, especially in the survival of motor neurons. Mutations in this gene have been associated with spinal muscular atrophy with respiratory distress type 1 (SMARD1) and Charcot-Marie-Tooth disease type 2S (CMT2S).

Methods

We conducted a systematic literature search using the PubMed database to identify studies published up to April 1st, 2023, that investigated the association between IGHMBP2 mutations and SMARD1 or CMT2S. We compared the non-truncating mutations and truncating mutations of the IGHMBP2 gene and selected high-frequency mutations of the IGHMBP2 gene.

Results

We identified 52 articles that investigated the association between IGHMBP2 mutations and SMARD1/CMT2S. We found 6 hotspot mutations of the IGHMBP2 gene. The truncating mutations in trans were all associated with SMARD1.

Conclusion

This study provides evidence that the complete LOF mechanism of the IGHMBP2 gene defect may be an important cause of SMARD1.

Severe Infantile Axonal Neuropathy with Respiratory Failure Caused by Novel Mutation in X-Linked LAS1L Gene

LAS1L encodes a nucleolar ribosomal biogenesis protein and is also a component of the Five Friends of Methylated CHTOP (5FMC) complex. Mutations in the LAS1L gene can be associated with Wilson−Turner syndrome (WTS) and, much more rarely, severe infantile hypotonia with respiratory failure. Here, we present an eighteen-month old boy with a phenotype of spinal muscular atrophy with respiratory distress (SMARD). By applying WES, we identified a novel hemizygous synonymous variant in the LAS1L gene inherited from an unaffected mother (c.846G > C, p.Thr282=). We suggest that the identified variant impairs the RNA splicing process. Furthermore, we proved the absence of any coding regions by qPCR and sequencing cDNA using amplicon deep sequencing and Sanger sequencing methods. According to the SMARD phenotype, severe breathing problems causing respiratory insufficiency, hypotonia, and feeding difficulties were observed in our patient from the first days of life. Remarkably, our case is the second described patient with a SMARD-like phenotype due to a mutation in the LAS1L gene and the first with a variant impacting splicing.

Diagnostic Odyssey and Application of Targeted Exome Sequencing in the Investigation of Recurrent Infant Deaths in a Syrian Consanguineous Family: a Case of Spinal Muscular Atrophy with Respiratory Distress Type 1

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare autosomal recessive disorder caused by a defect in the immunoglobulin mu binding protein 2 (IGHMBP2) gene, leading to motor neuron degeneration. We identified an infant with SMARD1 by targeted exome sequencing from a consanguineous Syrian family having a history of recurrent infant deaths. The patient initially presented intrauterine growth retardation, poor sucking, failure to thrive, and respiratory failure at the age of two months, and an inborn error of metabolism was suspected at first. Over a period of one month, the infant showed rapid progression of distal muscular weakness with hand and foot contractures, which were suggestive of neuromuscular disease. Using targeted exome sequencing, the mutation in IGHMBP2 was confirmed, although the first report was normal. Targeted exome sequencing enabled identification of the genetic cause of recurrent mysterious deaths in the consanguineous family. Additionally, it is suggested that a detailed phenotypic description and communication between bioinformaticians and clinicians is important to reduce false negative results in exome sequencing.

Spinal Muscular Atrophy With Respiratory Distress Type 1-A Child With Atypical Presentation

The authors report a child with spinal muscular atrophy with respiratory distress type 1 (SMARD1). She presented atypically with hypothyroidism and heart failure due to septal defects that required early heart surgery and microcephaly in association with cerebral atrophy and thin corpus collosum. The subsequent asymmetrical onset of diaphragmatic paralysis, persistent hypotonia, and generalized muscle weakness led to the suspicion of spinal muscular atrophy with respiratory distress type 1. Sanger sequencing confirmed a compound heterozygous mutation in the Immunoglobulin Mu Binding Protein 2 (IGHMBP2) gene, with a known mutation c.2362C > T (p.Arg788*) and a novel frameshift mutation c.2048delG (p.Gly683A1afs*50). Serial nerve conduction study and electromyography confirmed progressive sensorimotor polyneuropathy and neuronopathy. In summary, this case report describes a child with spinal muscular atrophy with respiratory distress type 1 also with congenital cardiac disease and endocrine dysfunction, expanding the phenotypic spectrum of this condition. A high index of suspicion is needed in diagnosing this rare condition to guide the management and genetic counseling.

Distal Spinal Muscular Atrophy: An Overlooked Etiology of Weaning Failure in Children with Respiratory Insufficiency

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is a rare autosomal recessive neuromuscular disorder that involves the anterior horn motor neurons. It is a disease with a poor prognosis presenting with progressive distal motor weakness and respiratory insufficiency from diaphragmatic paralysis followed by distal muscle weakness before 6 months of age. With the intent to spread the awareness of this rare and life-threatening disease, we report a 2.5-month-old female infant with a subsequent diagnosis of SMARD1, who was admitted in our pediatric intensive care unit with chief complaint of progressive respiratory distress and poor feeding.