Two Sibling Cases of Spastic Paraplegia-45 with a Novel Pathogenic Variant in NT5C2 Gene: Concomitant RYR1 Gene in One Sibling.

Introduction: Hereditary spastic paraplegia (SPG) is a genetically and clinically heterogeneous group of rare neurodegenerative disorders. SPG45 is the AR inherited type of complicated SPG, which is due to a mutation in the NT5C2 gene. Case Presentation: Two sisters, aged 8 and 4, exhibited delayed motor development since early childhood. They also experienced learning difficulties, dysarthric speech, ataxia, nystagmus, strabismus, and spasticity in their extremities. Additionally, brisk deep tendon reflexes were observed in their upper and lower limbs, and they exhibited positive pathological reflexes. Whole-exome sequencing identified a previously unidentified homozygous mutation in the NT5C2 gene, leading to the diagnosis of SPG45 in both siblings. A mutation in the RYR1 gene associated with malignant hyperthermia was also detected in one of the siblings, necessitating ongoing monitoring. Discussion/Conclusion: To the best of our knowledge, we report the first case of a patient with coexistence of the NT5C2 gene and the RYR1 gene.

Phenotype-Genotype Correlation of a Cohort of Patients with Congenital Myopathy: A Single Centre Experience from India.

Background: Congenital myopathies (CMs) are a diverse group of inherited muscle disorders with broad genotypic and phenotypic heterogeneity. While the literature on CM is available from European countries, comprehensive data from the Indian subcontinent is lacking. Objectives: This study aims to describe the clinical and histopathological characteristics of a cohort of genetically confirmed CMs from India and attempts to do phenotype-genotype correlation. Methods: A retrospective chart review of genetically confirmed CMs was evaluated between January 2016 and December 2020 at the neuromuscular clinic. The clinical, genetic, and follow-up data were recorded in a pre-structured proforma as per the medical records, and the data was analyzed. Results: A total of 31(M: F = 14 : 17) unrelated patients were included. The median age at onset and duration of illness are 2.0(IQR:1-8) years and 6.0(IQR:3-10) years respectively. Clinical features observed were proximodistal weakness (54.8%), facial weakness (64.5%), and myopathic facies (54.8%), followed by ptosis (33.3%), and ophthalmoplegia (19.4%). Muscle histopathology was available in 38.7% of patients, and centronuclear myopathy was the most common histopathology finding. The pathogenic genetic variants were identified in RYR1 (29.0%), DNM2 (19.4%), SELENON (12.9%), KBTBD13 (9.7%), NEB (6.5%), and MYPN (6.5%) genes. Novel mutations were observed in 30.3% of the cohort. Follow-up details were available in 77.4% of children, and the median duration of follow-up and age at last follow-up was 4.5 (Range 0.5-11) years and 13 (Range 3-35) years, respectively. The majority were ambulant with minimal assistance at the last follow-up. Mortality was noted in 8.3% due to respiratory failure in Centronuclear myopathy 1 and congenital myopathy 3 with rigid spines (SELENON). Conclusion: This study highlights the various phenotypes and patterns of genetic mutations in a cohort of pediatric patients with congenital myopathy from India. Centronuclear myopathy was the most common histological classification and the mutations in RYR1 followed by DNM2 gene were the common pathogenic variants identified. The majority were independent in their activities of daily living during the last follow-up, highlighting the fact that the disease has slow progression irrespective of the genotype.

Treatment and nursing care of a patient diagnosed with malignant hyperthermia after general anesthesia: a case report.

Malignant hyperthermia (MH), characterized by severe myoclonus, pyrexia, tachycardia, hypertension, elevated muscle enzymes, and hypercapnia, often occurs in patients with congenital deformities or genetic disorders. Although the reported incidence rate is as low as 1:5000 to 1:100,000, patients with MH exhibit rapid aggravation and an elevated mortality rate. Thus, MH is associated with substantial perioperative risk. Successful treatment of patients with MH largely depends on early diagnosis and timely effective treatment. This clinical report provides a detailed description of a patient with newly diagnosed MH who developed a rapid rise in body temperature, end-tidal carbon dioxide, and heart rate during maxillary osteotomy. After successful rescue, the patient recovered smoothly during the postoperative period, indicating the importance of intraoperative monitoring, early diagnosis, effective treatment, and postoperative monitoring. This case is expected to serve as a reference for future interventions and healthcare practices in managing other patients with MH.

One case of congenital myopathy caused by new mutation of RYR1 gene and literature review.

OBJECTIVE: To report a case of congenital myopathy caused by RYR1 gene complex heterozygous mutation and analyze the pathogenicity of the mutation. Method The clinical manifestation, laboratory examination, imaging findings, muscle pathology and gene test results of a child with congenital myopathy were analyzed retrospectively. Combined with literature review, it is analyzed and discussed. Result The child, female, was admitted to hospital because of "dyspnea for 22 min after asphyxia resuscitation". The main manifestations are low muscle tension, the original reflex cannot be drawn out, the trunk and proximal muscles are weak, and the tendon reflex is not drawn out. The pathological signs were negative. The electrolyte of blood liver and kidney function, blood thyroid and blood ammonia were not abnormal, and creatine kinase increased temporarily. Electromyography suggests myogenic damage. Whole exome sequencing showed that there was a new compound heterozygous variation in RYR1 gene c.14427_ 14429del/c.14138C＞T.Western blot showed that the expression of RYR1 protein in patients was significantly lower than that in normal controls. Conclusion The compound heterozygous variation of RYR1 gene c.14427 was reported for the first time in China_ 14429del/c.14138c > t is the pathogenic gene of the child. The new discovery of RYR1 gene spectrum was revealed, which expanded the RYR1 gene spectrum.

Successful Correction by Prime Editing of a Mutation in the RYR1 Gene Responsible for a Myopathy.

We report the first correction from prime editing a mutation in the RYR1 gene, paving the way to gene therapies for RYR1-related myopathies. The RYR1 gene codes for a calcium channel named Ryanodine receptor 1, which is expressed in skeletal muscle fibers. The failure of this channel causes muscle weakness in patients, which leads to motor disabilities. Currently, there are no effective treatments for these diseases, which are mainly caused by point mutations. Prime editing allows for the modification of precise nucleotides in the DNA. Our results showed a 59% correction rate of the T4709M mutation in the RYR1 gene in human myoblasts by RNA delivery of the prime editing components. It is to be noted that T4709M is recessive and, thus, persons having a heterozygous mutation are healthy. These results are the first demonstration that correcting mutations in the RYR1 gene is possible.

Effect of terminal sire line and timing second vaccination on effectiveness of immunocastration, performance, and carcass and meat quality.

Performance (from 10 weeks until slaughter), carcass and meat quality, and effectiveness of immunocastration was compared in crossbred offspring of stress positive (BP+) and negative (BP-) Belgian Piétrain and Canadian Duroc (CD) given the second vaccination of Improvac® at different times (4, 6, 8 weeks before slaughter). CD offspring had a significantly higher daily gain (DG) and feed intake (DFI), and lower predicted lean meat percentage (LMP) and dressing yield compared to BP+ and BP-, while feed conversion ratio (FCR) did not differ. CD offspring had significantly lower drip loss and higher pHi, intramuscular fat content than BP+ and BP- (except for pHi). No significant effect of vaccination time on DG nor FCR was observed. Predicted LMP tended to increase as time-post injection decreased, while meat quality was minor affected. Earlier vaccination had no effect on the effectiveness of immunocastration based on testosterone and GnRH-binding.

Performance and carcass, loin and ham quality in crossbreds from three terminal sire lines.

This study was designed to compare performance, carcass and meat quality of crossbred of a hybrid sow x three sire lines, i.e. stress positive Belgian Piétrain (BP), stress negative French Piétrain (FP) and Canadian Duroc (CD). BP offspring had a significantly higher carcass yield (p < .001) and lean meat content (p < .001) in comparison with FP, which was higher than CD. BP offspring had significantly lower pH (p < .05), water-holding capacity (WHC) (p < .001) and intramuscular fat (IMF) (p < .001) content in the loin compared to FP and CD, but these meat quality parameters, with the exception of pH, were superior for CD as compared to FP. In accordance with loin quality, pHi, pHu, WHC and IMF of BP were significantly lower (p < .05) compared to CD in the fresh and cooked ham. Most often, FP offspring could not be differentiated from the other offspring, with the exception of cooking loss of the cooked ham. Trained and consumer taste panels resulted in no significant differences (p > .1) in sensory attributes, however, consumers preffered CD based on ranking.

Parental mosaicism in RYR1-related Central Core Disease.

Myopathies due to mutations in the skeletal muscle ryanodine receptor (RYR1) gene are amongst the most common non-dystrophic neuromuscular disorders and have been associated with both dominant and recessive inheritance. Several cases with apparently de novo dominant inheritance have been reported. Here we report two siblings with features of Central Core Disease (CCD) born to unaffected parents. Genetic testing revealed a heterozygous dominant RYR1 c.14582G>A (p. Arg4861His) mutation previously identified in other CCD pedigrees. The variant was absent in blood from the asymptomatic mother but detected at low but variable levels in blood- and saliva-derived DNA from the unaffected father, suggesting that this mutation has arisen as a paternal post-zygotic de novo event. These findings suggest that parental mosaicism should be considered in RYR1-related myopathies, and may provide one possible explanation for the marked intergenerational variability seen in some RYR1 pedigrees.

Long term oral Dantrolene Improved Muscular Symptoms in a Malignant Hyperthermia Susceptible Individual.

This case report describes a female with p.Lys4876Arg amino acid change in the ryanodine receptor type 1 (RYR1) and a sibling who died of malignant hyperthermia (MH) during anesthesia. After her diagnosis as MH susceptible, this patient was administered low-dose dantrolene daily for greater than 25 years for treatment of chronic muscle spasm and pain in her lower extremities and back limiting sleep. Her creatine phosphokinase (CPK) was as high as 2390 IU/L during labor and 900 IU at rest. With 25 mg dantrolene daily, muscle cramps were eliminated, and sleep was improved. Gait instability was noted with dantrolene in the morning, but not when taken at bedtime. There was no evidence of liver injury. This case suggests that low dose dantrolene by mouth could be considered for the treatment of chronic muscle pain in individuals with MH susceptibility.

RYR1-related rhabdomyolysis: A common but probably underdiagnosed manifestation of skeletal muscle ryanodine receptor dysfunction.

Mutations in the skeletal muscle ryanodine receptor (RYR1) gene are associated with a wide spectrum of inherited myopathies presenting throughout life. Malignant hyperthermia susceptibility (MHS)-related RYR1 mutations have emerged as a common cause of exertional rhabdomyolysis, accounting for up to 30% of rhabdomyolysis episodes in otherwise healthy individuals. Common triggers are exercise and heat and, less frequently, viral infections, alcohol and drugs. Most subjects are normally strong and have no personal or family history of malignant hyperthermia. Heat intolerance and cold-induced muscle stiffness may be a feature. Recognition of this (probably not uncommon) rhabdomyolysis cause is vital for effective counselling, to identify potentially malignant hyperthermia-susceptible individuals and to adapt training regimes. Studies in various animal models provide insights regarding possible pathophysiological mechanisms and offer therapeutic perspectives.

The effects of ryanodine receptor (RYR1) mutation on natural killer cell cytotoxicity, plasma cytokines and stress hormones during acute intermittent exercise in pigs.

Stress susceptibility has been mapped to a single recessive gene, the ryanodine receptor 1 (RYR1) gene or halothane (Hal) gene. Homozygous (Hal(nn)), mutated pigs are sensitive to halothane and susceptible to Porcine Stress Syndrome (PSS). Previous studies have shown that stress-susceptible RYR1 gene mutated homozygotes in response to restraint stress showed an increase in natural killer cell cytotoxicity (NKCC) accompanied by more pronounced stress-related hormone and anti-inflammatory cytokine changes. In order to determine the relationship of a RYR1 gene mutation with NKCC, plasma cytokines and stress-related hormones following a different stress model - exercise - 36 male pigs (representing different genotypes according to RYR1 gene mutation: NN, homozygous dominant; Nn, heterozygous; nn, homozygous recessive) were submitted to an intermittent treadmill walking. During the entire experiment the greatest level of NKCC and the greatest concentrations of interleukin (IL-) 6, IL-10, IL-12, interferon (IFN-)γ and tumor necrosis factor-α and stress-related hormones (adrenaline, prolactin, beta-endorphin) were observed in nn pigs, and the greatest concentration of IL-1 and growth hormone in NN pigs. Immunostimulatory effects of intermittent exercise on NKCC in nn pigs were concomitant with increases in IL-2, IL-12 and IFN-γ, the potent NKCC activators. Our findings suggest that stress-susceptible pigs RYR1 gene mutated pigs develop a greater level of NKCC and cytokine production in response to exercise stress. These results suggest that the heterogeneity of immunological and neuroendocrine response to exercise stress in pigs could be influenced by RYR1 gene mutation.

Exertional Heat Stroke and Susceptibility to Malignant Hyperthermia in an Athlete: Evidence for a Link?

OBJECTIVE: To describe the possible association (pathophysiologic and clinical features) between exertional heat stroke (EHS) and malignant hyperthermia (MH). BACKGROUND: Both EHS and MH are acute and life-threatening disorders. It has repeatedly been shown that EHS can occur in well-trained patients with known MH-associated mutation in the RYR1 gene in the absence of any extreme environmental conditions or extreme physical activity, thereby supporting a possible link between EHS and MH. In this case, a highly trained 30-year-old male athlete suddenly collapsed while running. He had initial hyperthermia (40.2°C) and progressive multiple organ failure requiring medical management in an intensive care unit. After he recovered completely, a maximal exercise test was performed and showed an obvious abnormality of oxidative metabolism in muscle; genetic analysis of the RYR1 gene identified a heterozygous missense variation p.K1393R. Consequently, the athlete was given appropriate information and allowed to progressively return to sport competition. DIFFERENTIAL DIAGNOSIS: Doping, use of drugs and toxic agents, exercise-associated hyponatremia, exertional heat illness. TREATMENT: Initial management started with the basic resuscitative guidelines of airway, breathing, and circulation (intubation). Cooling, administration of fresh frozen plasma, and intensive rehydration resulted in improvement. UNIQUENESS: To our knowledge, ours is the first description of this MH mutation (p.K1393R) in the RYR1 gene that was associated with exertional rhabdomyolysis involving a dramatic impairment of oxidative metabolism in muscle. CONCLUSIONS: Common features are shared by EHS and MH. Careful attention must therefore be paid to athletes who experience EHS, especially in temperate climates or when there are no other predisposing factors.

A novel large deletion in the RYR1 gene in a Belgian family with late-onset and recessive core myopathy.

We report a novel and particularly unusual type of mutation, namely, large deletion in the RYR1 gene, in a Belgian family with myopathy: Patients were found to be compound heterozygous and presented a clinico-pathological phenotype characterized by late-onset and recessive myopathy with cores. We depict the clinical, electrophysiological, pathological and molecular genetic characteristics of family members. To date, large deletions in the RYR1 gene have been reported in only two cases. Both involved different mutations and, in sharp contrast to our cases, presented with a very early-onset, neonatal, and a very severe or lethal phenotype. Overview of reported clinico-pathologic phenotypes, also highlights the rarity of combined late-onset/recessive co-occurrence in this group of myopathies with cores. Finally, this report underlines the broadening spectrum in this group of myopathologic disorders and highlights the concept of 'RYR1-associated/related core myopathies'.

RYR1-related malignant hyperthermia with marked cerebellar involvement - a paradigm of heat-induced CNS injury?

Heat-induced CNS injury has been recognized for more than 50 years but the biological basis for the marked selectivity of CNS damage is currently uncertain. We present clinical, imaging, autopsy and genetic findings of a 14-year-old male who developed fatal cerebellar swelling in the course of a malignant hyperthermia (MH) episode caused by triggering anaesthetics. Unaccustomed intense exercise in the days prior to general anaesthesia was a probable confounding factor for the MH reaction. Autopsy findings demonstrated pronounced degeneration of cerebellar Purkinje cells. Post mortem genetic analysis revealed a mutation (c.6502G>A; p.Val2168Met) in the skeletal muscle ryanodine receptor (RYR1) gene previously associated with the MH trait. RYR1 mutations appear to be associated with heat-induced CNS injury in a distribution compatible with known expression pattern of the RyR1 isoform in cerebellar Purkinje cells. Recent exercise in genetically predisposed individuals may prime abnormal muscle prior to general anaesthesia and contribute to the severity of MH reactions.

The effects of ryanodine receptor 1 (RYR1) mutation on plasma cytokines and catecholamines during prolonged restraint in pigs.

In the current study, plasma cytokines, including interleukin (IL) 1, IL-2, IL-6, IL-10, IL-12, interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) and catecholamines (adrenaline and noradrenaline) were evaluated during 4h restraint and recovery phase in 60 male pigs. Blood samples were collected from three groups of pigs representing different RYR1 genotypes, namely NN homozygotes (wild-type), Nn heterozygous and nn homozygous (mutant). The 4h restraint evoked an increase in plasma cytokine concentrations in each of the RYR1 genotype groups. During the restraint, the greatest concentrations of plasma IL-6, IL-10, IL-12 and TNF-α in nn homozygous pigs and IFN-γ in NN homozygous were observed. Interleukin 1, IL-2, IL-10, and TNF-α measures were positively intercorrelated in each of the three RYR1 genotype group. A positive correlation was seen between all measured cytokines (with the exception of IL-6) and plasma catecholamine concentrations in Nn heterozygous and nn homozygous pigs. The results suggest that of the cytokine parameters evaluated, IL-6, IL-10, IL-12 and TNF-α of the nn homozygous group seem to show a stronger stress-related response as compared with those of the other two (NN and Nn) groups.