An Infant with Congenital Nemaline Myopathy and Hypertrophic Cardiomyopathy

Pediatric Nemaline Myopathy: A Systematic Review Using Individual Patient Data

Nemaline myopathy is a skeletal muscle disease that affects 1 in 50 000 live births. The objective of this study was to develop a narrative synthesis of the findings of a systematic review of the latest case descriptions of patients with NM. A systematic search of MEDLINE, Embase, CINAHL, Web of Science, and Scopus was performed using Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines using the keywords pediatric, child, NM, nemaline rod, and rod myopathy. Case studies focused on pediatric NM and published in English between January 1, 2010, and December 31, 2020, in order to represent the most recent findings. Information was collected about the age of first signs, earliest presenting neuromuscular signs and symptoms, systems affected, progression, death, pathologic description, and genetic changes. Of a total of 385 records, 55 case reports or series were reviewed, covering 101 pediatric patients from 23 countries. We review varying presentations in children ranging in severity despite being caused by the same mutation, in addition to current and future clinical considerations relevant to the care of patients with NM. This review synthesizes genetic, histopathologic, and disease presentation findings from pediatric NM case reports. These data strengthen our understanding of the wide spectrum of disease seen in NM. Future studies are needed to identify the underlying molecular mechanism of pathology, to improve diagnostics, and to develop better methods to improve the quality of life for these patients.

Respiratory treatment in a patient with nemaline myopathy

Respiratory involvement of nemaline myopathy is evident on the diaphragm and intercostal muscles function. The present case study aimed to describe the characteristics of the respiratory physiotherapeutic treatment in a patient with nemaline myopathy. Here, we describe a case of a 43-yearold woman with nemaline myopathy undergoing pulmonary rehabilitation during short hospital admission for an acute exacerbation. At the time of hospitalisation, the patient was already under oxygen therapy (1 L/min) and noninvasive home ventilation using bi-level positive airway pressure with a nasal interface. Supplementary therapeutic exercises were implemented in addition to daily nasal noninvasive ventilation. At discharge, ultrasound examination revealed increased diaphragm trophism if compared with data obtained at hospital admission.

Congenital myopathies are mainly associated with a mild cardiac phenotype

BACKGROUND

To evaluate the prevalence of cardiac involvement in patients with congenital myopathies and the association to specific genotypes.

METHODS

We evaluated patients with physical examination, electrocardiogram, echocardiography, and 48-h Holter monitoring. Follow-up was performed for major events.

RESULTS

We included 130 patients, 55 men (42%), with a mean age of 34 ± 17 years. A genetic diagnosis was established in 97 patients (75%). Right bundle branch block was observed in three patients: 2/34 patients with a ryanodine receptor 1 (RYR1) and 1/6 with a tropomyosin two gene (TPM2) gene mutation. Echocardiography showed left-ventricular hypertrophy in five patients: 2/17 and 3/34 patients with a Dynamin 2 (DNM2) and a RYR1 mutation, respectively. One patient with a myosin heavy-chain (MYH7) mutation had dilated cardiomyopathy and heart failure. On Holter monitoring, frequent ventricular premature contractions were observed in one patient with a DNM2 mutation. Two patients with a TPM2 and a RYR1 mutation, respectively, had a single short run of non-sustained ventricular tachycardia. Atrioventricular nodal re-entry tachycardia was observed in a 20-year-old man with an actin 1 gene mutation. During follow-up (median 8.4 years), four patients died, all of non-cardiac causes.

CONCLUSION

Congenital myopathies are generally associated with a mild cardiac phenotype. Our findings substantiate the literature and indicate that, except for patients with specific genotypes, such as MYH7 and TTN mutations, repeated cardiac assessments can be minimized, given a normal initial cardiac screening at time of diagnosis.

[Two cases of nemaline myopathy presenting with hypertrophy of distal limbs with prominent asymmetry]

Nemaline myopathy commonly presents with symmetrical proximal weakness. Here we report two cases of nemaline myopathy presenting with distal dominant involvement with prominent asymmetry. Case 1 was a 37-year-old man who recalled frequently falling down and had right calf atrophy since he was 3-years-old. He had right calf muscle atrophy and weakness and steppage gait; his cardiopulmonary function was normal. Case 2 was a 35-year-old man with right calf muscle atrophy and weakness since childhood. He had right dominant distal leg weakness and atrophy together with respiratory failure and started noninvasive positive pressure ventilation. He also developed cardiomyopathy and died from acute respiratory failure due to pneumonia at age 39. Both cases harbored compound heterozygous nebulin (NEB) mutations with c.20131 C>T:p.Arg6711Trp and a nonsense mutation. Nemaline myopathy associated with NEB mutations can present as distal dominant myopathy with prominent asymmetry.

Review of Cardiac Disease in Nemaline Myopathy

OBJECTIVES

Little is known about the type, frequency, severity, treatment, and outcome of cardiac disease in nemaline myopathy. This review summarizes and discusses findings concerning the type, prevalence, diagnosis, treatment, and outcome of cardiac involvement in nemaline myopathy.

METHODS

Review of publications about nemaline myopathy and cardiac disease.

RESULTS

Altogether, 35 patients with nemaline myopathy with cardiac disease were identified. Age at presentation ranged from 0 to 62 years. In 30 individuals whose gender was described, 22 were male and eight were female. Onset was congenital in 16 patients, infantile in five, and adult in four. Nine patients presented with dilated cardiomyopathy, six with hypertrophic cardiomyopathy, and one with nonspecific cardiomyopathy. Among those with cardiomyopathy, four developed heart failure. One patient experienced sudden cardiac death. A ventricular septal defect was described in two patients. Cardiac treatment included drugs for heart failure (eight patients), implantable cardioverter-defibrillator implantation (one patient), and heart transplant (three patients). Four patients received noninvasive positive-pressure ventilation and two continuous positive-pressure ventilation. The outcome was fatal in 11 patients.

CONCLUSIONS

Cardiac disease in nemaline myopathy manifests as cardiomyopathy leading to heart failure. If respiratory muscles are affected, the right side of the heart may be secondarily involved. Early detection of cardiac involvement is essential since effective treatment for cardiac disease in nemaline myopathy may be available.

Potential causes of sudden cardiac death in nemaline myopathy

ᅟ

A Premature Stop Codon in MYO18B is Associated with Severe Nemaline Myopathy with Cardiomyopathy

Background: Nemaline myopathies (NM) are rare and severe muscle diseases characterized by the presence of nemaline bodies (rods) in muscle fibers. Although ten genes have been implicated in the etiology of NM, an important number of patients remain without a molecular diagnosis.

Objective: Here we describe the clinical and histopathological features of a sporadic case presenting with severe NM and cardiomyopathy. Using exome sequencing, we aimed to identify the causative gene.

Results: We identified a homozygous nonsense mutation in the last exon of MYO18B, leading to a truncated protein lacking the most C-terminal part. MYO18B codes for an unconventional myosin protein and it is mainly expressed in skeletal and cardiac muscles, two tissues severely affected in the patient. We showed that the mutation does not impact on mRNA stability. Immunostaining and Western blot confirmed the absence of the full-length protein.

Conclusion: We propose MYO18B as a novel gene associated with nemaline myopathy and cardiomyopathy.

Nemaline myopathy in a newborn infant: a rare muscle disorder

Nemaline myopathy (NM) is a genetically and clinically heterogeneous muscle disorder, defined by the presence of characteristic nemaline bodies on muscle biopsy. The disease has a wide spectrum of phenotypes, ranging from forms with neonatal onset and fatal outcome to asymptomatic forms. The neonatal form is severe and usually fatal. The clinical variability, with differing age of onset and severity of symptoms makes the diagnosis difficult during infancy. There is no curative treatment. L-tyrosine may prevent aspiration by reducing pharyngeal secretions and drooling. Most of the patients die from respiratory and cardiac failure. This article discusses a newborn infant who presented with generalized weakness and respiratory failure. Partial response to L-tyrosine treatment was noted. The case is worth presenting to remind clinicians of congenital myopathies in the differential diagnosis of floppy infant during neonatal period and to emphasize the importance of muscle biopsy in diagnosis.

Nemaline myopathy with dilated cardiomyopathy in childhood

We present a case of a 9-year-old boy with nemaline myopathy and dilated cardiomyopathy. The combination of nemaline myopathy and cardiomyopathy is rare, and this is the first reported case of dilated cardiomyopathy associated with childhood-onset nemaline myopathy. A novel mutation, p.W358C, in ACTA1 was detected in this patient. An unusual feature of this case was that the patient's cardiac failure developed during early childhood with no delay of gross motor milestones. The use of a β-blocker did not improve his clinical course, and the patient died 6 months after diagnosis of dilated cardiomyopathy. Congenital nonprogressive nemaline myopathy is not necessarily a benign disorder: deterioration can occur early in the course of dilated cardiomyopathy with neuromuscular disease, and careful clinical evaluation is therefore necessary.

Nemaline myopathy and non-fatal hypertrophic cardiomyopathy caused by a novel ACTA1 E239K mutation

A twenty-year old male presented with diffuse limb muscle weakness and exertional dyspnea since childhood. The diagnosis of nemaline myopathy was given based on the muscle pathology findings that revealed nemaline rods on light and electron microscopy and discovery of a novel mutation, E239K, in ACTA1. Incidentally, the patient had hypertrophic cardiomyopathy (HCM) as shown by echocardiography. In nemaline myopathy, a few cases of HCM have been reported, albeit rarely and always fatal, but only one patient had ACTA1 mutation. This present report describes an infantile onset of nemaline myopathy with a milder clinical course and non-fatal HCM as compared with previous cases, showing clinical diversity in skeletal and cardiac manifestations of conditions associated with ACTA1 mutations.