Child neuromuscular disease in southern Norway. Prevalence, age and distribution of diagnosis with special reference to "non-Duchenne muscular dystrophy"

Prevalence and Classification of Pediatric Neuromuscular Disorders in the Central Region of Portugal

Neuromuscular disorders are a group of rare heterogenous diseases with profound impact on quality of life, for which overall pediatric prevalence has rarely been reported. The purpose of this study was to determine the point prevalence of pediatric neuromuscular disorders and its subcategories in the central region of Portugal. Retrospective case identification was carried out in children with neuromuscular disorders seen between 1998 and 2020 from multiple data sources. Demographics, clinical and molecular diagnoses were registered. On January 1, 2020, the point overall prevalence in the population <18 years of age was 41.20/100 000 (95% confidence interval 34.51-49.19) for all neuromuscular disorders. The main case proportion were genetic disorders (95.7%). We found a relatively higher occurrence of limb-girdle muscular dystrophies, congenital myopathies, and spinal muscular atrophy and a slightly lower occurrence of Duchenne muscular dystrophy, hereditary spastic paraparesis, and acquired neuropathies compared to previous studies in other countries. Molecular confirmation was available in 69.5% of pediatric neuromuscular patients in our cohort.Total prevalence is high in comparison with the data reported in the only previous study on the prevalence of pediatric neuromuscular disorders in our country. Our high definitive diagnostic rate underscores the importance of advances in investigative genetic techniques, particularly new sequencing technologies, in the diagnostic workup of neuromuscular patients.

Prevalence of morbidities across the lifespan for adults with spinal muscular atrophy: a retrospective cohort study

BACKGROUND

Recently approved treatments for spinal muscular atrophy (SMA) may shift clinical care priorities to secondary complications associated with SMA-related aging. To date, there is little knowledge about the natural history of morbidities across the adult lifespan for SMA. The objective of this study was to identify the prevalence and odds ratio (OR) of various morbidities among adults with vs. without SMA prior to SMA-related treatment.

METHODS

This was a retrospective cohort study that accessed Medicare fee-for-service and commercial claims data from 01/01/2008-12/22/2016. Data from adults ≥ 18 years old with SMA and without SMA matched (1:200 case:control) on demographics, region, and study entry year were included. The prevalence of 30 morbidities across physiologic systems (e.g., cardiovascular, metabolic, musculoskeletal, urinary) and mental health disorders was examined. Age- and sex-adjusted OR was estimated using logistic regression for each morbidity and effect modification by age and sex was tested.

RESULTS

There were 2,427 adults with SMA (mean [SD] age, 59.7 [17.4] years; 49.0% female) and 484,528 matched adults without SMA. Adults with vs. without SMA had a higher prevalence and adjusted OR of all 30 morbidities, ranging from OR = 1.61 (95% CI = 1.45-1.80) for hypothyroidism to OR = 7.80 (95% CI = 7.10-8.57) for fluid/electrolyte disorders. There was effect modification by age for 24 morbidities. The OR was highest for the youngest age group (18-40 years; OR range, 2.38 to 117.7; all P < 0.05) and declined with older age groups, but still remained significantly elevated in the oldest age group (≥ 75 years; OR range, 1.30 to 5.96; all P < 0.05).

CONCLUSIONS

The limitations of this study are that evidence of morbidities were limited to diagnostic claims and information on SMA type and symptoms or onset were not available. In conclusion, adults with SMA had a higher and earlier prevalence of a variety of morbidities across physiological systems and mental health disorders.

Spinal muscular atrophy carrier frequency in Saudi Arabia

BACKGROUND

Spinal Muscular Dystrophy (SMA) is one of the leading causes of death in infants and young children from heritable diseases. Although no large-scale popultion-based studies have been done in Saudi Arabia, it is reported that the incidence of SMA is higher in the Saudi population partly because of the high degree of consanguineous marriages.

METHODS

The final analysis included 4198 normal volunteers aged between 18 and 25 years old, 54.7% males, and 45.3% females. Whole blood was spotted directly from finger pricks onto IsoCode StixTM and genomic DNA was isolated using one triangle from the machine. To discern the SMN1 copy number independently from SMN2, Multiplex PCR with Dral restriction fragment analysis was completed. We used the carrier frequency and population-level data to estimate the prevalence of SMA in the population using the life-table method.

RESULTS

This data analysis showed the presence of one copy of the SMN1 gene in 108 samples and two copies in 4090 samples, which resulted from a carrier frequency of 2.6%. The carrier frequency was twofold in females reaching 3.7% compared to 1.6% in males. 27% of participants were children of first-cousin marriages. We estimated the birth incidence of SMA to be 32 per 100,000 birth and the total number of people living with SMA in the Kingdom of Saudi Arabia to be 2265 of which 188 are type I, 1213 are type II, and 8,64 are type III.

CONCLUSION

The SMA carrier rate of 2.6% in Saudi control subjects is slightly higher than the reported global frequency of 1.25 to 2% with links to the high degree of consanguinity.

Opportunities for an early recognition of spinal muscular atrophy in primary care: a nationwide, population-based, study in Italy

BACKGROUND

Spinal muscular atrophy (SMA) is a rare genetic disease with a broad spectrum of severity. Although an early diagnosis of SMA is crucial to allow proper management of patients, the diagnostic delay is still an issue. Therefore, this study aimed to investigate the clinical correlates of SMA among primary care patients.

METHODS

The Health Search Database (HSD) was adopted. To estimate the prevalence and incidence rate of SMA, a cohort study was conducted on the population (aged ≥6 years) being registered in HSD from 1 January 2000 up to 31 December 2019. To investigate the clinical correlates of SMA, a nested case-control study was performed. SMA cases have been classified according to a clinically based iterative process as "certain", "probable" or "possible". To test the association between clinical correlates and SMA cases a multivariate conditional logistic regression model was estimated.

RESULTS

The SMA prevalence combining "certain", "probable" and "possible" cases was 5.1 per 100,000 in 2019 (i.e. 1.12 per 100,000 when limited to "certain" cases), while the yearly incidence rate ranged from 0.12 to 0.56 cases per 100,000. Comparing "certain" cases with matched controls, the presence of neurology visits (OR = 6.5; 95% CI: 1.6-25.6) and prescription of electromyography (OR = 4.6; 95% CI: 1.1-18.7) were associated with higher odds of SMA diagnosis.

CONCLUSIONS

Our findings suggest that primary care databases may be used to enhance the early identification of SMA. Additional efforts are needed to exploit the electronic health records of general practitioners to allow early recognition of SMA.

Corrigendum: A Systematic Review and Meta-Analysis of the Prevalence of Congenital Myopathy

[This corrects the article DOI: 10.3389/fneur.2021.761636.].

Epidemiological investigation of spinal muscular atrophy in Japan

BACKGROUND

International reporting of epidemiological surveys of spinal muscular atrophy (SMA) in Japan has been limited to Shikoku, despite the epidemiology of the disease in countries worldwide becoming clearer. Treatments of 5q-SMA have been developed, and epidemiological studies are needed.

PURPOSE

This study aimed to conduct a nationwide epidemiological survey of SMA in Japan to clarify the actual situation of SMA in Japan.

METHOD

Patients with all clinical types of SMA, including neonates and adults, were selected from 1,005 medical facilities in Japan.

RESULTS

As of December 2017, the actual number of reported patients with SMA was 658 and the genetic testing rate was 79.5%. The estimated number of patients was 1,478 (95% confidence interval (CI), 1,122-1,834), with a prevalence of 1.17 (95%CI, 0.89-1.45) per 100,000 people and an incidence of 0.51 (95%CI, 0.32-0.71) per 10,000 live births. Incidence rates of 5q-SMA by clinical type were 0.27 (95%CI, 0.17-0.38) and 0.08 (95%CI, 0.04-0.11) per 10,000 live births for type 1 and 2, respectively, in cases with a definitive diagnosis by genetic testing. We found that 363 cases (82.7%) occurred less than 2 years and 88 (20.0%) occurred age of 2 months old or under.

CONCLUSION

This study clarifies the prevalence and incidence of SMA in Japan. As infantile onset accounts for most cases of SMA, newborn screening and subsequent treatment are important to save lives.

A Systematic Review and Meta-Analysis of the Prevalence of Congenital Myopathy

Background: Congenital myopathy constitutes a heterogeneous group of orphan diseases that are mainly classified on the basis of muscle biopsy findings. This study aims to estimate the prevalence of congenital myopathy through a systematic review and meta-analysis of the literature.

Methods: The PubMed, MEDLINE, Web of Science, and Cochrane Library databases were searched for original research articles published in English prior to July 30, 2021. The quality of the included studies was assessed by a checklist adapted from STrengthening the Reporting of OBservational studies in Epidemiology (STROBE). To derive the pooled epidemiological prevalence estimates, a meta-analysis was performed using the random effects model. Heterogeneity was assessed using the Cochrane Q statistic as well as the I² statistic.

Results: A total of 11 studies were included in the systematic review and meta-analysis. Of the 11 studies included, 10 (90.9%) were considered medium-quality, one (9.1%) was considered low-quality, and no study was assessed as having a high overall quality. The pooled prevalence of congenital myopathy in the all-age population was 1.62 (95% CI, 1.13–2.11) per 100,000, while the prevalence in the child population was 2.76 (95% CI, 1.34–4.18) per 100,000. In the pediatric population, the prevalence among males was 2.92 (95% CI, −1.70 to 7.55) per 100,000, while the prevalence among females was 2.47 (95% CI, −1.67 to 6.61) per 100,000. The prevalence estimates of the all-age population per 100,000 were 0.20 (95% CI 0.10–0.35) for nemaline myopathy, 0.37 (95% CI 0.21–0.53) for core myopathy, 0.08 (95% CI −0.01 to 0.18) for centronuclear myopathy, 0.23 (95% CI 0.04–0.42) for congenital fiber-type disproportion myopathy, and 0.34 (95% CI, 0.24–0.44) for unspecified congenital myopathies. In addition, the prevalence estimates of the pediatric population per 100,000 were 0.22 (95% CI 0.03–0.40) for nemaline myopathy, 0.46 (95% CI 0.03–0.90) for core myopathy, 0.44 (95% CI 0.03–0.84) for centronuclear myopathy, 0.25 (95% CI −0.05 to 0.54) for congenital fiber-type disproportion myopathy, and 2.63 (95% CI 1.64–3.62) for unspecified congenital myopathies.

Conclusions: Accurate estimates of the prevalence of congenital myopathy are fundamental to supporting public health decision-making. The high heterogeneity and the lack of high-quality studies highlight the need to conduct higher-quality studies on orphan diseases.

The Antisense Oligonucleotide Nusinersen for Treatment of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a rare, autosomal recessive neuromuscular degenerative disease characterized by loss of spinal cord motor neurons leading to progressive muscle wasting. The most common pathology results from a homozygous disruption in the survival motor neuron 1 (SMN1) gene on chromosome 5q13 via deletion, conversion, or mutation. SMN2 is a near duplicate of SMN1 that can produce full-length SMN mRNA transcripts, but its overall production capability of these mRNA transcripts is lower than that seen in SMN1. This leads to lower levels of functional SMN protein within motor neurons. The FDA approved nusinersen in December 2016 to treat SMA associated with SMN1 gene mutation. It is administered directly to the central nervous system by intrathecal injection. An antisense oligonucleotide (ASO) drug, nusinersen, provides an upcoming and promising treatment option for SMA and represents a novel pharmacological approach with a mechanism of action relevant for other neurodegenerative disorders. Nusinersen begins with four initial loading doses that are followed by three maintenance doses per year. Three major studies (CHERISH, ENDEAR, and NURTURE) have shown to improve motor function in early and late-onset individuals and reduce the chances of ventilator requirements in pre-symptomatic infants. Studies investigating the timing of drug delivery in mouse models of SMA report the best outcomes when drugs are delivered early before any significant motor function is lost. Nusinersen is a novel therapeutic approach with consistent results in all three studies and is proof of the novel concept for treating SMA and other neurodegenerative disorders in the future.

Global epidemiology of Duchenne muscular dystrophy: an updated systematic review and meta-analysis

Background

Duchenne Muscular Dystrophy (DMD) is a rare disorder caused by mutations in the dystrophin gene. A recent systematic review and meta-analysis of global DMD epidemiology is not available. This study aimed to estimate the global overall and birth prevalence of DMD through an updated systematic review of the literature.

Methods

MEDLINE and EMBASE databases were searched for original research articles on the epidemiology of DMD from inception until 1st October 2019. Studies were included if they were original observational research articles written in English, reporting DMD prevalence and/or incidence along with the number of individuals of the underlying population. The quality of the studies was assessed using a STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) checklist adapted for observational studies on rare diseases. To derive the pooled epidemiological prevalence estimates, a meta-analysis was performed using random-effects logistic models for overall and birth prevalence and within two different underlying populations (i.e. all individuals and in males only), separately. Heterogeneity was assessed using Cochran’s Q-test along with its derived measure of inconsistency I².

Results

A total of 44 studies reporting the global epidemiology of DMD were included in the systematic review and only 40 were included in the meta-analysis. The pooled global DMD prevalence was 7.1 cases (95% CI: 5.0–10.1) per 100,000 males and 2.8 cases (95% CI: 1.6–4.6) per 100,000 in the general population, while the pooled global DMD birth prevalence was 19.8 (95% CI:16.6–23.6) per 100,000 live male births. A very high between-study heterogeneity was found for each epidemiological outcome and for all underlying populations (I² > 90%). The test for funnel plot asymmetry suggested the absence of publication bias. Of the 44 studies included in this systematic review, 36 (81.8%) were assessed as being of medium and 8 (18.2%) of low quality, while no study was assessed as being of high quality.

Conclusions

Generating epidemiological evidence on DMD is fundamental to support public health decision-making. The high heterogeneity and the lack of high quality studies highlights the need to conduct better quality studies on rare diseases.

Epidemiological study and genetic characterization of inherited muscle diseases in a northern Spanish region

Background

Inherited muscle diseases are a group of rare heterogeneous muscle conditions with great impact on quality of life, for which variable prevalence has previously been reported, probably due to case selection bias. The aim of this study is to estimate the overall and selective prevalence rates of inherited muscle diseases in a northern Spanish region and to describe their demographic and genetic features. Retrospective identification of patients with inherited muscle diseases between 2000 and 2015 from multiple data sources. Demographic and molecular data were registered.

Results

On January 1, 2016, the overall prevalence of inherited muscle diseases was 59.00/ 100,000 inhabitants (CI 95%; 53.35–65.26). Prevalence was significantly greater in men (67.33/100,000) in comparison to women (50.80/100,000) (p = 0.006). The highest value was seen in the age range between 45 and 54 (91.32/100,000) years. Myotonic dystrophy type 1 was the most common condition (35.90/100,000), followed by facioscapulohumeral muscular dystrophy (5.15/100,000) and limb-girdle muscular dystrophy type 2A (2.5/100,000).

Conclusions

Prevalence of inherited muscle diseases in Navarre is high in comparison with the data reported for other geographical regions. Standard procedures and analyses of multiple data sources are needed for epidemiological studies of this heterogeneous group of diseases.

Measuring the tilt and slant of Chinese handwriting in primary school students: A computerized approach

BACKGROUND

"Horizontal strokes should be level and vertical strokes should be straight" is a common guideline in the teaching of Chinese handwriting. Measuring deviations in level horizontal and straight vertical strokes in students' Chinese handwriting is usually assessed manually. However, this task is time-consuming and may have inconsistent outcomes when judged by different people. In this paper, we aim to formulate a method to automatically evaluate the tilt and slant degrees of students' Chinese handwriting using digital handwriting tablets. Furthermore, we analyze the relationship between the tilt and slant features of students' Chinese handwriting and other demographic and handwriting features.

METHODS

Five hundred and ninety-one primary school students from grades 1 to 6 were recruited in Hong Kong. Before the assessment, a grid paper was attached to a digital handwriting tablet. The participants were then asked to copy 90 Chinese characters from a template to the grid paper. Their handwriting processes were recorded as two-dimensional points and then analyzed. The tilt and slant of the students' handwriting were calculated based on the inclination level of their horizontal and vertical strokes. Linear regressions between slant/tilt degree of the manuscripts and other handwriting features were performed. The students' demographic information was also explored.

RESULTS

Slant was found to be significantly correlated to Gender (p < 0.001) and tilt×standard deviation of pen pressure (p < 0.001). Tilt was found to be significantly correlated to ground time (p < 0.001), slant (p < 0.001) and slant×special education need (p = 0.021).

CONCLUSIONS

Our results demonstrate the relationship between slant, tilt and Chinese handwriting performance in primary school children. Slant and tilt can be adopted as an indicator in students' special education need diagnosis, as tilt level in the students' Chinese handwriting was related to ground time and slant× special education need, while slant is related to tilt×standard deviation of pen pressure and female students. These findings may also inspire ways to increase special education need students' writing speed.

Prevalence, incidence and carrier frequency of 5q-linked spinal muscular atrophy - a literature review

Spinal muscular atrophy linked to chromosome 5q (SMA) is a recessive, progressive, neuromuscular disorder caused by bi-allelic mutations in the SMN1 gene, resulting in motor neuron degeneration and variable presentation in relation to onset and severity. A prevalence of approximately 1-2 per 100,000 persons and incidence around 1 in 10,000 live births have been estimated with SMA type I accounting for around 60% of all cases. Since SMA is a relatively rare condition, studies of its prevalence and incidence are challenging. Most published studies are outdated and therefore rely on clinical rather than genetic diagnosis. Furthermore they are performed in small cohorts in small geographical regions and only study European populations. In addition, the heterogeneity of the condition can lead to delays and difficulties in diagnosing the condition, especially outside of specialist clinics, and contributes to the challenges in understanding the epidemiology of the disease. The frequency of unaffected, heterozygous carriers of the SMN1 mutations appears to be higher among Caucasian and Asian populations compared to the Black (Sub-Saharan African ancestry) population. However, carrier frequencies cannot directly be translated into incidence and prevalence, as very severe (death in utero) and very mild (symptom free in adults) phenotypes carrying bi-allelic SMN1 mutations exist, and their frequency is unknown. More robust epidemiological data on SMA covering larger populations based on accurate genetic diagnosis or newborn screening would be helpful to support planning of clinical studies, provision of care and therapies and evaluation of outcomes.

Prevalence of muscular dystrophies: a systematic literature review

BACKGROUND

Determining the prevalence of neuromuscular disorders for the general population is important to identify the scope of burden on society and enable comparisons with other health conditions. This systematic review aims to identify and collate the findings of studies published between 1960 and 2013 on the prevalence of all types of muscular dystrophies.

SUMMARY

Relevant articles were identified through electronic database searches and manual searches of reference lists. There were 38 articles from across 19 countries that met the inclusion criteria. The total combined prevalence for all muscular dystrophies for studies classified as having a low risk of bias ranged between 19.8 and 25.1 per 100,000 person-years. Myotonic dystrophy (0.5-18.1 per 100,000), Duchenne muscular dystrophy (1.7-4.2) and facioscapulohumeral muscular dystrophy (3.2-4.6 per 100,000) were found to be the most common types of disorder. There was wide variation in study methodology, case ascertainment, and verification procedures and populations studied, all of which may contribute to the wide prevalence range, in addition to the likely variation in prevalence by country. Key Messages: Greater consistency in the conduct and reporting of neuroepidemiological studies is urgently needed to enable comparisons to be made between studies, countries, and over time.

Spinal muscular atrophies

Spinal muscular atrophies (SMA) are genetic disorders characterized by degeneration of lower motor neurons. The most frequent form is caused by mutations of the survival motor neuron 1 gene (SMN1). The identification of this gene greatly improved diagnostic testing and family-planning options of SMA families. SMN plays a key role in metabolism of RNA. However, the link between RNA metabolism and motor neuron degeneration remains unknown. A defect in mRNA processing likely generates either a loss of function of some critical RNA or abnormal transcripts with toxic property for motor neurons. Mutations of SMN in various organisms highlighted an essential role of SMN in motor axon and neuromuscular junction development or maintenance. The quality of life of patients has greatly improved over recent decades through the improvement of care and management of patients. In addition, major advances in translational research have been made in the field of SMA. Various therapeutic strategies have been successfully developed aiming at acting on SMN2, a partially functional copy of the SMN1 gene which remains present in patients. Drugs have been identified and some are already at preclinical stages. Identifying molecules involved in the SMA degenerative process should represent additional attractive targets for therapeutics in SMA.

Quick MLPA test for quantification of SMN1 and SMN2 copy numbers

Spinal muscular atrophy (SMA) is an autosomal recessive disease caused in about 95% of SMA patients by homozygous deletion of the survival motor neuron 1 (SMN1) gene or its conversion to the highly homologous SMN2 gene. In the majority of cases, disease severity correlates inversely with increased SMN2 copy number. Because of the comparatively high incidence of healthy carriers and severity of the disease, detection of sequence alterations and quantification of SMN1 and SMN2 copy numbers are essential for exact diagnosis and genetic counselling. Several assays have been developed for this purpose. Multiplex ligation-dependent probe amplification (MLPA) is a versatile technique for relative quantification of different nucleic acid sequences in a single reaction. Here, we establish a quick MLPA-based assay for the detection of SMN1 and SMN2 copy numbers with high specificity and low complexity.

A simple multiplex real-time PCR methodology for the SMN1 gene copy number quantification

Spinal muscular atrophy (SMA) is an autosomal recessive disease caused, in about 95% of SMA cases, by homozygous deletion of the survival motor neuron 1 (SMN1) gene or its conversion to the highly homologous SMN2 gene. The molecular diagnosis of SMA is usually carried out by a PCR-Restriction fragment length polymorphism (RFLP) approach. However, this approach is not useful for identification of healthy deletion carriers. TaqMan technology is one of the most reliable and widely adopted techniques for the SMN1 copy number evaluation. However, several limitations of this technique have been described. Particularly, DNA extraction methods and accurate template quantification have been shown to be critical for reliable results. In this work, we set up a reliable, highly reproducible, and easy-to-perform TaqMan technology-based protocol to obtain the SMN1 gene copy number assessment. We demonstrate that PCR amplification of both target gene and reference gene in the same reaction mix, instead of separated mixes, greatly reduces reported criticisms of simplex TaqMan technology. The multiplex real-time PCR we describe allows interlaboratory samples and data exchange, without the need to equalize the DNA isolation technique. Further, the protocol described below requires fewer replica tests than the simplex methodology does, leading to reduced overall cost for the diagnostic assay.

Epidemiology of myotonic dystrophy type 1 (Steinert disease) in Belgrade (Serbia)

The aim of this study was to estimate the incidence and prevalence of myotonic dystrophy type 1 (DM1) in Belgrade during the period 1983-2002. The patients who had DM1 were ascertained through hospital records from all neurological departments in Belgrade during 1983-2002. The molecular genetic analysis was performed in all patents included in the study. We identified 101 DM1 patients (52 males and 49 females). The average annual incidence rate of DM1 in Belgrade for the period observed was 2.0/1,000,000 (95% confidence interval (CI), 0.3-8.3), 2.1/1,000,000 (95% CI, 0.3-8.3) for males and 2.0/1,000,000 (95% CI, 0.3-8.3) for females. The highest age-specific DM1 incidence was registered in the age group 20-49: 3.4/1,000,000 (95% CI, 0.5-7.6), 4.0/1,000,000 (95% CI, 1.1-10.2) in males and 2.5/1,000,000 (95% CI, 0.5-7.6) in females. In the population of Belgrade, a cumulative probability of acquiring DM1 was 1 per 8621 for men and 1 per 9259 for women (1 per 8940 of the population for both sexes). The prevalence of DM1 in Belgrade on 31 December 2002 was 5.3/100,000 (95% CI, 4.2-6.6).

Genetic risk assessment in carrier testing for spinal muscular atrophy

As evidenced by the complete absence of a functionally critical sequence in exon 7, approximately 94% of individuals with clinically typical spinal muscular atrophy (SMA) lack both copies of the SMN1 gene at 5q13. Hence most carriers have only one copy of SMN1. Combining linkage and dosage analyses for SMN1, we observed unaffected individuals who have two copies of SMN1 on one chromosome 5 and zero copies of SMN1 on the other chromosome 5. By dosage analysis alone, such individuals, as well as carriers of non-deletion disease alleles, are indistinguishable from non-carrier individuals. We report that approximately 7% of unaffected individuals without a family history of SMA have three or four copies of SMN1, implying a higher frequency of chromosomes with two copies of SMN1 than previously reported. We present updated calculations for disease and non-disease allele frequencies and we describe how these frequencies can be used for genetic risk assessment in carrier testing for SMA.

Lung function in children with Duchenne's muscular dystrophy

Duchenne's muscular dystrophy (DMD), characterized by gradually developing muscular weakness, leads to respiratory symptoms and reduced lung function. We aimed to assess lung function in 25 patients with DMD in relationship to age and muscular function. The 25 boys, mean age 13 years, comprized patients in southern Norway with DMD, taking part in an epidemiological follow-up study. None had chronic respiratory disease. Lung function was measured by maximum expiratory flow-volume loops and whole body plethysmography, and repeated after 1 year (n= 14). Lung function was reduced compared to predicted values for healthy children. Forced expiratory volume in 1 sec (FEV1)% predicted and forced vital capacity (FVC)% predicted correlated (significantly) inversely to age. FEV1 and FVC decreased annually 5.61 and 4.2% of predicted, respectively. Absolute values of FVC (litres) and FEV1 (1 sec(-1)) increased until mean age 14 years, decreasing thereafter. Values in % predicted decreased steadily throughout the age range (6-19 years). Lung function correlated closely to upper limb muscle function.

Lung function measurements in young children with spinal muscle atrophy; a cross sectional survey on the effect of position and bracing

BACKGROUND

Spinal muscular atrophy (SMA) affects respiratory muscles, which in addition to progressive scoliosis leads to respiratory impairment. Children with developing scoliosis are usually treated with spinal bracing to delay the progress.

AIMS

To assess the impact of body position and application of spinal bracing on lung function during tidal breathing in children with SMA.

METHODS

Lung function was determined by tidal flow volume loops and passive respiratory mechanics (single breath occlusion technique) in all eight children in southern Norway with SMA type I and II, in both the sitting and supine position. Additional measurements were performed with and without bracing in five children. Muscle strength was assessed by the Brooks scale.

RESULTS

Tidal expiratory volume (V(E)) and compliance of the respiratory system (CRS) tended to be higher in the sitting compared to the supine position, but this was not statistically significant. However, applying bracing in the sitting position significantly reduced V(E). The highest values of CRS and V(E) were found in the sitting position without bracing.

CONCLUSION

Impairment of tidal respiration must be considered when applying spinal bracing in very young children developing scoliosis with SMA.

Response to influenza immunisation during treatment for cancer

AIMS

To assess the annual risk of influenza infection in children with cancer and the immunogenicity of a trivalent split virus influenza vaccine in these children.

METHODS

Eighty four children with cancer were tested for susceptibility to the circulating strains of influenza virus in autumn 1995 and 1996. Non-immunised children were reassessed the following spring for serological evidence of natural infection. Forty two patients received two doses of influenza vaccine. These children were receiving continuing chemotherapy for acute lymphoblastic leukaemia or were within six months of completing chemotherapy.

RESULTS

Among the 84 children tested for influenza virus susceptibility only 8% of patients were fully protected (antibody titres >/= 40) against all three of the prevalent influenza virus strains; 33% were susceptible to all three viruses. Evidence of acquired natural infection was seen in 30% of unimmunised patients. Among immunised susceptible patients, 66% made some protective response to the vaccine and 55% showed protective antibody titres to all three viral strains following vaccination. Older age was associated with increased response to the H1N1 and H3N2 vaccine components, but total white cell count or neutrophil count at immunisation, type of cancer, or length of time on treatment for acute lymphoblastic leukaemia did not affect response.

CONCLUSIONS

Most children with cancer studied were at risk of influenza infection. A significant response to immunisation was seen, supporting annual influenza vaccination for children being treated for cancer.

Genetic epidemiology of Duchenne and Becker muscular dystrophy in Slovenia

Most population studies on Duchenne (DMD) and Becker (BMD) muscular dystrophies predated the discovery of the gene and its product dystrophin. The diagnosis of these conditions and consequent epidemiological estimates were therefore limited to clinical criteria. In our study of the Slovene population the prevalence and cumulative incidence of DMD and BMD were calculated by including additional diagnostic tests: deletion screening in the dystrophin gene as well as dystrophin immunocytochemistry. The minimal prevalence rates, 2.9/100,000 for DMD, 1.2/100,000 for BMD, and the minimal cumulative DMD incidence rate of 13.8/100,000 are in the range of lower estimates compared to studies world-wide. However, we found a high BMD cumulative incidence rate of 5.7/100,000 and a high proportion of BMD versus DMD cumulative incidence rate (41.3%). Our results imply that the epidemiological figures for BMD might have been underestimated in the past.

De-novo mutation in hereditary motor and sensory neuropathy type I

Isolated cases of hereditary motor and sensory neuropathy type I (HMSN I, Charcot-Marie-Tooth disease type 1) have been thought to be most frequently autosomal recessive. We have found that a recently discovered duplication in chromosome 17, responsible for most cases of autosomal dominant HMSN I, is present as a de-novo mutation in 9 out of 10 sporadic patients. This finding has important implications for genetic counselling of isolated patients with HMSN I.

Epidemiology of neuromuscular disorders in the under-20 population in Bologna Province, Italy

A retrospective epidemiological survey of the principal neuromuscular disorders was undertaken in the population under the age of 20 yr in Bologna city and province. The incidence of Duchenne muscular dystrophy (DMD) proved to be 25.8 x 10(-5), that is, comparable with the outcome of neonatal screening studies. The incidence of spinal muscular atrophy (SMA) was very high (11.2 x 10(-5), probably the result of our greater awareness and recognition of this disorder. The prevalence of neuromuscular disorders in the 0-19 yr population is 1.5 times that in the general population; that of DMD is 28 x 10(-5) vs 6.3 x 10(-5) and that of the SMA 6.5 x 10(-5) vs 1.2 x 10(-5). Our results indicate that neuromuscular disorders, particularly DMD and SMA I and II, have a much higher prevalence in the first two decades of life than is generally thought. Awareness of the higher prevalence of neuromuscular disorders among the under-20s is essential to the adequate planning of medical services.

Prevalence of type I spinal muscular atrophy in North Dakota

In order to establish the incidence and prevalence of type I spinal muscular atrophy (SMA Werdnig-Hoffmann disease) in North Dakota, we reviewed the death certificates for the past 8 years. Between 1980 and 1987 the prevalence of was 1.5 per 10,000. The incidence was 1 in 6,720. This suggests a carrier frequency of 1 in 41 in North Dakota with a gene frequency of 0.0122. In North Dakota, type I spinal muscular atrophy appears to be 3 to 10 times more common than in other locations.

Prevalence and incidence of Becker muscular dystrophy

We measured the prevalence and incidence of Becker muscular dystrophy in the Northern Health Region of England, UK. Patients were identified from the records of the Regional Neurological Centre and Muscular Dystrophy Group laboratories, Newcastle upon Tyne, and by writing to local doctors. We used cDNA probes and/or dystrophin immunolabelling of muscle-biopsy samples to prove the diagnosis of all cases. Results were compared with the known prevalence and incidence of Duchenne muscular dystrophy. 73 patients alive and resident in the Northern Health Region were identified, giving a prevalence rate of 2.38/100,000. This compares with a prevalence of Duchenne muscular dystrophy of 2.48/100,000. The cumulative birth incidence of Becker muscular dystrophy (at least 1 in 18 450 male live births) was about one third that of Duchenne muscular dystrophy (1 in 5618 male live births), suggesting that the disorder is more common than previously thought.

Population frequencies of inherited neuromuscular diseases--a world survey

A survey of the world literature, involving over 150 reported studies, of the population frequencies of various inherited neuromuscular diseases has been carried out. Data are presented for the commoner forms of muscular dystrophy (Duchenne, Becker, facioscapulohumeral, limb girdle), myotonic dystrophy and congenital myotonias, proximal spinal muscular atrophies, and the hereditary motor and sensory neuropathies. A conservative estimate of the overall prevalence among both sexes is around 286 x 10(-6), that is 1 in 3500 of the population may be expected to have a disabling inherited neuromuscular disease presenting in childhood or in later life. If severe disorders manifest only in infancy and early childhood (e.g. Werdnig-Hoffmann disease and severe congenital muscular dystrophy) and the rare forms of dystrophy and myopathy are also included, then the overall prevalence could well exceed 1 in 3000.

Population data on acute infantile and chronic childhood spinal muscular atrophy in Warsaw

This study provides epidemiological data on acute infantile (ASMA) and chronic childhood spinal (CSMA) muscular atrophy in Warsaw for the period 1976-1985. All calculations are based on the assumption that ASMA and CSMA result from mutations at two different gene loci. The incidence of ASMA and CSMA was 1 in 19474 live births with a corresponding gene and carrier frequency of 714 x 10(-5) and 1 in 70, respectively. The prevalence of CSMA for the year 1985 was 1.26 x 10(-5). These figures are higher than in similar studies in other countries. This fact might be connected with the careful ascertainment in this study.