Genotype‒phenotype correlation in recessive DNAJB4 myopathy

Protein aggregate myopathies can result from pathogenic variants in genes encoding protein chaperones. DNAJB4 is a cochaperone belonging to the heat shock protein-40 (HSP40) family and plays a vital role in cellular proteostasis. Recessive loss-of-function variants in DNAJB4 cause myopathy with early respiratory failure and spinal rigidity, presenting from infancy to adulthood. This study investigated the broader clinical and genetic spectrum of DNAJB4 myopathy. In this study, we performed whole-exome sequencing on seven patients with early respiratory failure of unknown genetic etiology. We identified five distinct pathogenic variants in DNAJB4 in five unrelated families of diverse ethnic backgrounds: three loss-of-function variants (c.547C > T, p.R183*; c.775C > T, p.R259*; an exon 2 deletion) and two missense variants (c.105G > C, p.K35N; c.181A > G, p.R61G). All patients were homozygous. All affected individuals exhibited early respiratory failure, and patients from three families had rigid spine syndrome with axial weakness in proportion to appendicular weakness. Additional symptoms included dysphagia, ankle contractures, scoliosis, neck stiffness, and cardiac dysfunction. Notably, J-domain missense variants were associated with a more severe phenotype, including an earlier age of onset and a higher mortality rate, suggesting a strong genotype–phenotype correlation. Consistent with a loss of function, the nonsense variants presented decreased stability. In contrast, the missense variants exhibited normal or increased stability but behaved as loss-of-function variants in yeast complementation and TDP-43 disaggregation assays. Our findings suggest that DNAJB4 is an emerging cause of myopathy with rigid spine syndrome of variable age of onset and severity. This diagnosis should be considered in individuals presenting with suggestive symptoms, particularly if they exhibit neck stiffness during infancy or experience respiratory failure in adults without significant limb muscle weakness. Missense variants in the J-domain may predict a more severe phenotype.

In amyotrophic lateral sclerosis (ALS), a recent double-blind placebo-controlled trial of acetyl-L-carnitine along with riluzole showed probable benefit in 42 patients compared with 40 patients who received placebo. Using an electrophysiologic measure devised to differentiate ALS from other neuromuscular conditions, a "splint-hand index" was devised and is reviewed. Analysis of skin in ALS may also be of interest, and there was a report of accumulation of fused in sarcoma protein in the epidermis of ALS patients. With regard to myasthenia gravis, there is another report that early treatment of ocular symptoms with corticosteroids may prevent the development of generalized symptoms. A new study of thymus histopathology in muscle-specific tyrosine kinase (MuSK) myasthenia gravis is covered and another article on the use of thymectomy. In Duchenne muscular dystrophy, the best method of administrating corticosteroids is still being debated, and a long-term study of daily versus intermittent prednisolone is reviewed. The study showed less sustained benefit from the intermittent prednisolone but with a better side effect profile. According to 2 recent reports, it seems that titin mutations may be an underrecognized cause of myopathy with early respiratory failure in adults. Keeping with the respiratory failure theme, there was also an interesting article on the long-term benefits and side effects of cyclosporine in patients with interstitial lung disease from antisynthetase syndrome. Finally, the spectrum of small fiber neuropathy may be expanding to include a causative role in some patients with fibromyalgia syndrome and in juveniles with diffuse pain and a possible autoimmune predisposition.

New disease allele and de novo mutation indicate mutational vulnerability of titin exon 343 in hereditary myopathy with early respiratory failure

EP.123Selenoprotein-related congenital myopathy in two siblings

Context: Rigid spine syndrome is rare in children. It is commonly observed in the end stage of the muscular dystrophies. Another entity called primary rigid spine or spinal muscular dystrophy syndrome, rigidity of spine is noted at the beginning of a muscle disease. The two conditions should be differentiated. Evidence Acquisition: The first child with primary rigid spine syndrome was observed in 1996. Twelve children were observed over the last eighteen years and were followed up regularly in the hospital under study. The children were diagnosed with rigid spine syndrome if there was restriction of the neck movements, particularly on the bending of the spine. The diagnosis was based on clinical features, biochemical tests, electrophysiological findings, imaging and muscle biopsy. Genetic tests were not available in the past, but were done recently in three children. Results: Twelve children (nine males and three females) were observed. Ten children had primary rigid spine and two had secondary rigid spine syndrome. Conclusions: The current study described twelve children with rigid spine syndrome from Oman; ten with primary rigid spine (rigid spinal muscular dystrophy) and two with secondary rigid spine syndrome. The condition is rare in children. Early neck stiffness is the key to diagnosis.

The role of pulmonary function before stem cell transplant as a potential risk factor for the development of early post-transplant respiratory failure and mortality is controversial. We conducted a retrospective analysis of the pretransplant pulmonary function of 2,852 patients who received their transplant between 1990 and 2001. Pretransplant FEV(1), FVC, total lung capacity (TLC), diffusing capacity of carbon monoxide (DL(CO)), and the alveolar-arterial oxygen tension difference P(A-a)O(2) were measured and assessed for association with development of early respiratory failure and mortality in Cox proportional hazard logistic models. In multivariate analyses, progressive decrease of all lung function parameters was associated with a stepwise increase in risk of developing early respiratory failure and mortality when assessed in independent models. On the basis of a significant correlation between FEV(1) and FVC (r = 0.81), FEV(1) and TLC (r = 0.61), and FVC and TLC (r = 0.80), and a lack of correlation between FEV(1) and DL(CO), we developed a pretransplant lung function score based on pretransplant FEV(1) and DL(CO) to determine the extent of pulmonary compromise before transplant. Multivariate analysis indicated that higher pretransplant lung function scores are associated with a significant increased risk for developing early respiratory failure (category II hazard ratio [HR], 1.4; category III HR, 2.2; category IV HR, 3.1; p < 0.001) and death (category II HR, 1.2; category III HR, 2.2; category IV HR, 2.7; p < 0.005). These results suggest that not only does compromised pretransplant lung function contribute to the risk for development of early respiratory failure and mortality but this risk may be estimated before transplant by grading the extent of FEV(1) and DL(CO) compromise.

The use of extracorporeal membrane oxygenation (ECMO) for severe acute respiratory failure (ARF) in adults is growing rapidly given recent advances in technology, even though there is controversy regarding the evidence justifying its use. Because ECMO is a complex, high-risk, and costly modality, at present it should be conducted in centers with sufficient experience, volume, and expertise to ensure it is used safely. This position paper represents the consensus opinion of an international group of physicians and associated health-care workers who have expertise in therapeutic modalities used in the treatment of patients with severe ARF, with a focus on ECMO. The aim of this paper is to provide physicians, ECMO center directors and coordinators, hospital directors, health-care organizations, and regional, national, and international policy makers a description of the optimal approach to organizing ECMO programs for ARF in adult patients. Importantly, this will help ensure that ECMO is delivered safely and proficiently, such that future observational and randomized clinical trials assessing this technique may be performed by experienced centers under homogeneous and optimal conditions. Given the need for further evidence, we encourage restraint in the widespread use of ECMO until we have a better appreciation for both the potential clinical applications and the optimal techniques for performing ECMO.

Pulmonary surfactant protein (SP)-B plays a vital role in the formation and function of surfactant in the lung. A genetic polymorphism (SP-B + 1580) is postulated to result in diminished activity of SP-B. The objective was to determine whether the SP-B + 1580 CC genotype is associated with an increased risk of respiratory failure and ARDS in adults with community-acquired pneumonia. Prospective cohort of adults diagnosed with community-acquired pneumonia. Hospital system. We enrolled 402 adults > or = 18 yrs of age with community-acquired pneumonia; 158 were white, 243 were African American, and one was Asian. Genotypic analysis was performed on DNA isolated from whole blood using polymerase chain reaction amplification and DdeI restriction enzyme digestion. We recorded the requirement for mechanical ventilation, the presence of acute respiratory distress syndrome (ARDS) or septic shock, and mortality. Sixty-three patients required mechanical ventilation, 12 patients developed ARDS, and 35 patients developed septic shock. Genotypic frequencies at the SP-B + 1580 site were T/T 183 of 402 (0.45), T/C 160 of 402 (0.40), and C/C 59 of 402 (0.15). Of the 59 patients who were C/C at the SP-B + 1580 site, 21 (0.356) required mechanical ventilation, compared with 26 of 160 patients (0.163) who were T/C and 16 of 183 (0.087) patients who were T/T (p < .001). ARDS developed in five of 59 (0.085) patients with the C/C genotype, compared with six of 160 (.038) patients with T/C and one of 183 patients with T/T (0.005, p < .009). Septic shock occurred in 12 of 59 (0.203) patients with the C/C genotype, compared with 13 of 160 (0.081) patients with T/C and ten of 183 (0.055) patients with T/T (p < .001). Mortality rate was not different between the three genotypes. Carriage of the C allele at the SP-B + 1580 site is associated with ARDS, septic shock, and the need for mechanical ventilation in adults with community-acquired pneumonia.

BackgroundHuman metapneumovirus (hMPV) is an emerging respiratory pathogen causing illnesses from mild upper respiratory infection to severe pneumonia, particularly in high-risk adults. Although primarily recognized in pediatrics, hMPV is increasingly reported as a cause of acute respiratory failure in adults with chronic lung disease and obesity.CaseA 58-year-old man with morbid obesity and chronic obstructive pulmonary disease presented with acute respiratory failure and viral septic shock. Molecular testing of bronchoalveolar lavage (BioFire® FilmArray®) identified human metapneumovirus type 1 as the sole pathogen. The patient required invasive mechanical ventilation, vasopressor support, and continuous renal replacement therapy. Vancomycin was discontinued for suspected nephrotoxicity, and systemic corticosteroids were introduced. Subsequent bronchoalveolar lavage cultures grew Streptococcus pneumoniae, confirming bacterial superinfection. With supportive management, the patient gradually improved, was extubated on day 9, and was discharged home in stable condition.ConclusionhMPV can trigger severe respiratory failure and multiorgan dysfunction in adults with chronic respiratory comorbidities. Early molecular diagnosis is crucial to guide management and limit unnecessary antimicrobial exposure. The absence of specific antivirals underscores the need for continued research into targeted treatments and preventive vaccines.

Rigid spine syndrome is a rare childhood-onset myopathy characterized by slowly progressive or non-progressive scoliosis, neck and spine contractures, hypotonia and respiratory insufficiency. Biallelic variants in SELENON account for most cases of rigid spine syndrome, however, the underlying genetic cause in some patients remains unexplained. We used exome and genome sequencing to investigate the genetic basis of rigid spine syndrome in patients without a genetic diagnosis. In five patients from four unrelated families, we identified biallelic variants in HMGCS1 (3-hydroxy-3-methylglutaryl-coenzyme A synthase). These included six missense variants and one frameshift variant distributed throughout HMGCS1. All patients presented with spinal rigidity primarily affecting the cervical and dorso-lumbar regions, scoliosis and respiratory insufficiency. Creatine kinase levels were variably elevated. The clinical course worsened with intercurrent disease or certain drugs in some patients; one patient died from respiratory failure following infection. Muscle biopsies revealed irregularities in oxidative enzyme staining with occasional internal nuclei and rimmed vacuoles. HMGCS1 encodes a critical enzyme of the mevalonate pathway and has not yet been associated with disease. Notably, biallelic hypomorphic variants in downstream enzymes including HMGCR and GGPS1 are associated with muscular dystrophy resembling our cohort's presentation. Analyses of recombinant human HMGCS1 protein and four variants (p.S447P, p.Q29L, p.M70T, p.C268S) showed that all mutants maintained their dimerization state. Three of the four mutants exhibited reduced thermal stability, and two mutants showed subtle changes in enzymatic activity compared to the wildtype. Hmgcs1 mutant zebrafish displayed severe early defects, including immobility at 2 days and death by Day 3 post-fertilisation and were rescued by HMGCS1 mRNA. We demonstrate that the four variants tested (S447P, Q29L, M70T and C268S) have reduced function compared to wild-type HMGCS1 in zebrafish rescue assays. Additionally, we demonstrate the potential for mevalonic acid supplementation to reduce phenotypic severity in mutant zebrafish. Overall, our analyses suggest that these missense variants in HMGCS1 act through a hypomorphic mechanism. Here, we report an additional component of the mevalonate pathway associated with disease and suggest biallelic variants in HMGCS1 should be considered in patients presenting with an unresolved rigid spine myopathy phenotype. Additionally, we highlight mevalonoic acid supplementation as a potential treatment for patients with HMGCS1-related disease.

The population frequency of AD polycystic kidney disease (ADPKD) has not been known with certainty. We hypothesized that more accurate population frequencies for typical (PKD1, PKD2) and atypical (GANAB, ALG9, DNAJB11 ALG5, IFT140, NEK8) ADPKD were possible using a computational approach. Initially, this study calculated the number of predicted pathogenic structural, null, and missense variants in the ADPKD-associated genes in gnomAD v.2.1.1, and compared this with disease-causing changes according to the ClinVar, HGMD, or LOVD databases. However, because of the difficulty assessing missense variant pathogenicity, ClinVar assessments were used instead for gnomAD v.4.1, which includes a larger cohort, and more structural and copy number data. Predicted pathogenic variants were found in the typical ADPKD genes in 1 in 314 people, with PKD1 and PKD2 changes present in 1 in 417 and 916, respectively, using ClinVar assessments of gnomAD v.4.1 variants and loss-of-function structural and copy number changes. Predicted pathogenic null and missense variants in the atypical ADPKD genes were found in 1 in 283 people in gnomAD v.4.1 using ClinVar. No pathogenic missense changes in the kinase domain of NEK8 previously-reported in monoallelic disease were present. Predicted pathogenic variants in the genes associated with typical and atypical ADPKD are more common than suspected previously. Predicted pathogenic variants are more common for atypical than for typical ADPKD, especially when loss-of-function structural and copy number variants are included.

Background The majority of missense variants in clinical genetic tests are classified as variants of uncertain significance. Prior research has shown that the deleterious effects and the subsequent molecular consequence of variants are often conserved among paralogous protein sequences within a gene family. Here, we systematically quantified on an exome-wide scale if the existence of pathogenic variants in paralogous genes at a conserved position could serve as evidence for the pathogenicity of a new variant. For the gene family of voltage-gated sodium channels where variants and expert-curated clinical phenotypes were available, we also assessed whether phenotype patterns of multiple disorders for each gene were also conserved across variant positions within the gene family. Methods We developed a framework that assesses the presence of pathogenic missense variants located in conserved residues across paralogous genes. We systematically mapped 2.5 million pathogenic and general population variants from the ClinVar, HGMD, and gnomAD databases onto a total of 9,990 genes and aligned them by gene families. We evaluated the quantity of classifiable amino acids by utilizing pathogenic variants identified in databases alone and then compared this assessment to the inclusion of paralogous pathogenic variants. We validated and quantified the evidence of conserved pathogenic paralogous variants in variant pathogenicity classification. Results Considering conserved pathogenic variants in paralogous genes, increased the number of classifiable variants 2.8-fold across the exome, compared to pathogenic variants in the gene of interest alone. The presence of a pathogenic variant in a paralogous gene is associated with a positive likelihood ratio of 8.32 for variant pathogenicity. The likelihood ratio was gene family-specific. Across ten genes encoding voltage-gated sodium channels and 22 expert-curated disorders, we identified cross-paralog correlated phenotypes based on 3D structure spatial position. For example, the established loss-of-function disorders SCN1A-associated Dravet syndrome, SCN2A-associated autism, SCN5A-associated Brugarda Syndrome, and SCN8A-associated neurodevelopmental disorder without seizures were correlated in their spatial variant position on structure. Finally, we show that phenotype integration in paralog variant selection improves variant classification. Conclusion Our results show that paralogous variants, in particular with phenotype information can enhance our understanding of variant effects.

eP061: Genetic risk for breast and ovarian cancer in a diverse and unselected population

Epilepsy with eyelid myoclonias and Sotos syndrome features in a patient with compound heterozygous missense variants in APC2 gene

Sir, Hereditary myopathy with early respiratory failure (HMERF) is a neuromuscular disease associated with aggregation of various proteins in muscle fibres and muscle degeneration (Fig. 1) and was described in detail in several families by Edstrom et al. (1990). Linkage analyses indicated that the disease locus was in the distal part of the long arm of chromosome 2 (Nicolao et al. , 1999). Titin was a candidate gene and a missense variant that segregated with the disease in …