A Case of GNE Myopathy Presenting a Rapid Deterioration during Pregnancy

Patient reported pregnancy and birth outcomes in genetic neuromuscular diseases

Pregnancy and birth in women with neuromuscular conditions has been associated with more rapid disease progression and obstetric complications. This study assessed the impact of functional status and specific diagnosis on patient reported pregnancy and birth outcomes in 26 genetic neuromuscular diseases. Pregnancy and birth outcomes were collected through electronic patient questionnaires and analysed by mobility group and diagnosis. Free text responses were grouped into themes. 721 pregnancies were reported by 305 women. Miscarriage (21% of pregnancies), caesarean delivery (38% of births) and instrumental vaginal delivery (19% of births) were all more frequent in respondents than in the general population (p<0.05), and were more common in those who were non-ambulant at conception than other mobility levels (p <0.05). Falls occurred during 42% of pregnancies and a deterioration in muscle strength during 43%. There was not an increased incidence of maternal complications, apart from maternal hypertension which was more common in limb girdle muscular dystrophy 2A/R1 (35%) and myotonic dystrophy (24%). Patients offered specific practical advice to prospective mothers. Women with neuromuscular conditions have a more complex antenatal and perinatal course than unaffected women. Prenatal counselling, specialist obstetric review and additional occupational therapy support should be considered.

Recent advances in establishing a cure for GNE myopathy

PURPOSE OF REVIEW

GNE myopathy is a rare autosomal recessive disease caused by biallelic variants in the GNE gene, which encodes an enzyme involved in sialic acid biosynthesis. No drugs are approved for the treatment of GNE myopathy. Following proof-of-concept of sialic acid supplementation efficacy in mouse models, multiple clinical trials have been conducted. Here, we review clinical trials of sialic acid supplementation therapies and provide new insights into the additional clinical features of GNE myopathy.

RECENT FINDINGS

Clinical trials of sialic acid supplementation have been conducted in Europe, the USA, Japan, and South Korea. Some clinical trials of NeuAc-extended release tablets demonstrated amelioration of decline in upper extremity muscle strength; however, no significant improvement was observed in phase 3 trials in Europe and USA. A phase 2 trial of ManNAc showed slowed decline of both upper and lower extremity strength. GNE myopathy patient registries have been established in Europe and Japan, and have provided information on extramuscular manifestations such as thrombocytopenia, respiratory dysfunction, and sleep apnea syndrome. Sensitive and reliable biomarkers, and a disease-specific functional activity scale, have also been investigated.

SUMMARY

We discuss recent advances in establishing a GNE myopathy cure, and discuss other prospective therapeutic options, including gene therapy.

Gene analysis and clinical features of 22 GNE myopathy patients

INTRODUCTION

GNE myopathy is an autosomal recessive distal myopathy caused by a biallelic mutation in UDP-N-acetylglucosamine 2-epomerase/N-acetylmannosamine kinase. In this study, we discuss the clinical features, pathological characteristics, genetic profiles, and atypical clinical manifestations of 22 Chinese GNE patients.

MATERIALS AND METHODS

Retrospective analysis was performed for GNE myopathy patients at our institute between 2005 and 2021. Histopathological analysis and gene testing were done according to standard protocols.

RESULTS

Molecular analysis revealed 14-reported and 7 novel mutations, including c.125G > A (p.P42Q), c.226G > A (p.V76I), c.970C > G (p.H324D), c.155A > G (p.D52G), c.1055G > A (p.R352H), c.1064G > A (p.G355E), and c.491 T > C (p.I164T) in GNE. D207V was the most frequent mutation showing an allele frequency of 25%. A total of 21 patients presented classic clinical manifestation, and only 1 patient had signs of proximal muscle weakness. A patient containing p.V603L and p.R160X mutations showed idiopathic thrombocytopenia and distal weakness. There were 4 female patients who experienced rapid deterioration after pregnancy.

DISCUSSION

Our study revealed 7 novel mutations in GNE, where p.D207V was shown as a potential hotspot mutation in Chinese patients. Idiopathic thrombocytopenia should be a concern in GNE myopathy patients. Twenty-seven percent of female patients experienced rapid deterioration during pregnancy or after delivery.

Genetic Appraisal of Hereditary Muscle Disorders In A Cohort From Mumbai, India

BACKGROUND

Hereditary muscle disorders are clinically and genetically heterogeneous. Limited information is available on their genetic makeup and their prevalence in India.

OBJECTIVE

To study the genetic basis of prevalent hereditary myopathies.

MATERIAL AND METHODS

This is a retrospective study conducted at a tertiary care center. The study was approved by the institutional ethics board. The point of the collection was the genetic database. The genetic data of myopathy patients for the period of two and half years (2019 to mid-2021) was evaluated. Those with genetic diagnoses of DMD, FSHD, myotonic dystrophies, mitochondriopathies, and acquired myopathies were excluded. The main outcome measures were diagnostic yield and the subtype prevalence with their gene variant spectrum.

RESULTS

The definitive diagnostic yield of the study was 39% (cases with two pathogenic variants in the disease-causing gene). The major contributing genes were GNE (15%), DYSF (13%), and CAPN3 (7%). Founder genes were documented in Calpainopathy and GNE myopathy. The uncommon myopathies identified were Laminopathy (0.9%), desminopathy (0.9%), and GMPPB-related myopathy (1.9%). Interestingly, a small number of patients showed pathogenic variants in more than one myopathy gene, the multigenic myopathies.

CONCLUSION

This cohort study gives hospital-based information on the prevalent genotypes of myopathies (GNE, Dysferlinopathy, and calpainopathy), founder mutations, and also newly documents the curious occurrence of multigenicity in a small number of myopathies.

Pregnancy in GNE myopathy patients: a nationwide repository survey in Japan

BACKGROUND

GNE myopathy is an autosomal recessive adult-onset distal myopathy. While a few case reports have described the progression of GNE myopathy during pregnancy, to our knowledge, none have examined disease progression after delivery or obstetric complications.

OBJECTIVE

This study aimed to reveal maternal complications, newborn complications, and the impact of pregnancy on disease progression in GNE myopathy patients.

METHODS

We conducted a questionnaire survey on pregnancy, delivery, and newborns involving female GNE myopathy patients who are currently registered in a national registry in Japan.

RESULTS

The response rate for the questionnaire survey was 60.0% (72/120). Of the 72 respondents, 44 (61.1%) had pregnancy experience (average, 1.8 pregnancies; 53 pregnancies before onset and 28 after onset). The incidence of threatened abortion was 26.9% among post-onset pregnancies, which was higher compared to those of the general Japanese population (p = 0.03). No other maternal or infant complications were commonly observed. Over 80% were unaware of changes in disease progression during pregnancy (mean age, 32.8 ± 3.5 years) or after delivery (32.9 ± 3.8 years), while 19.0% experienced disease exacerbation within a year after delivery (30.0 ± 1.0 years). Six patients developed myopathy within a year after delivery (29.7 ± 4.6 years), while none developed myopathy during pregnancy.

CONCLUSIONS

There were no serious maternal or newborn complications, and subjective progression did not differ during or after delivery in the majority of GNE myopathy patients. However, our findings suggest the importance of considering the possibility of threatened abortion and disease progression after delivery.

GNE Myopathy With Novel Mutations and Pronounced Paraspinal Muscle Atrophy

GNE myopathy is characterized by distal muscle weakness, and caused by recessive mutations in GNE. Its onset is characteristically in young adulthood, although a broad spectrum of onset age is known to exist. A large number of mutations in GNE are pathogenic and this clinical phenotype can be difficult to differentiate clinically from other late-onset myopathies. We describe two families with novel mutations in GNE, and describe their clinical and MRI features. We also describe the presence of striking paraspinal muscle involvement on MRI of the lumbar spine, which is an under-recognized feature of GNE myopathy.

Phenotypic stratification and genotype-phenotype correlation in a heterogeneous, international cohort of GNE myopathy patients: First report from the GNE myopathy Disease Monitoring Program, registry portion

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Patient registry is a valuable tool in international GNE myopathy research.

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The registry expands the knowledge of GNE myopathy genetics and epidemiology.

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The registry allows monitoring of the disease progression and discovering diversity.

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The data suggest possible genotype–phenotype correlation in GNE myopathy.

GNE myopathy is a rare distal myopathy, caused by mutations in the GNE gene, affecting sialic acid synthesis. Clinical presentation varies from asymptomatic early stage patients to severely debilitating forms. This first report describes clinical presentations and severity of the disease, using data of 150 patients collected via the on-line, patient-reported registry component of the GNE Myopathy Disease Monitoring Program (GNEM-DMP). Disease progression was prospectively analysed, over a 2-year period, using the GNE myopathy functional activity scale (GNEM-FAS). The average annual rates of decline in function were estimated at −9.6% and −3.2% in ambulant and non-ambulant patients respectively. 4.3% of participants became non-ambulant within one year. The mean time from onset to required use of a wheelchair was 11.9 years. Mean delay of genetic diagnosis from symptom onset was 5.2 years. Mutation specific analysis demonstrated genotype–phenotype relationships; i.e. p.Ala662Val may be associated with a more severe phenotype, compared to p.Val727Met. Patients with compound heterozygous mutation in epimerase and kinase domain appeared to have a more severe phenotype compared to patients with both mutations located within one domain. Acknowledging the limitations of the study, these findings suggest that the severity of the GNE mutations affects disease severity. The GNEM-DMP is a useful data collection tool, prospectively measuring the progression of GNE myopathy, which could play an important role in translational and clinical research and further understanding of genotype–phenotype correlations.

Clinical and Electrophysiological Findings in Hereditary Inclusion Body Myopathy Compared With Sporadic Inclusion Body Myositis

OBJECTIVE

To compare the clinical and electrophysiological findings in hereditary inclusion body myopathy (hIBM) and sporadic inclusion body myositis (sIBM) patients.

METHODS

We retrospectively identified 8 genetically proven hIBM patients and 1 DNAJB6 myopathy with pathological features of hIBM, and compared their clinical, electromyographic, and serological data with a group of 51 pathologically proven sIBM patients.

RESULTS

hIBM patients had a younger mean age of onset (36 vs. 60 years, P = 0.0001). Diagnostic delay was shorter in sIBM (6 vs. 15 years, P = 0.0003). Wrist flexors (P = 0.02), digit flexors (P = 0.01), digit extensors (P = 0.02), and quadriceps (P = 0.008) muscles were more frequently affected in sIBM. Fibrillation potentials were more common in sIBM patients (P = 0.03). Electrical myotonia was found in 4 hIBM patients, not significantly different from sIBM patients (P = 0.45). Creatinine kinase was higher in sIBM patients (799 vs 232, P = 0.03).

CONCLUSIONS

sIBM and hIBM seem to have similar electromyographic changes. The combination of clinical, serological, and histopathological findings can guide genetic testing to the final diagnosis.