Incidence of infantile spinal muscular atrophy on Shikoku Island of Japan

Burden of disease of spinal muscular atrophy linked to chromosome 5q (5q-SMA) in Colombia

OBJECTIVE

This article estimates the disease burden of 5q-SMA in Colombia by using the Disability-Adjusted Life Years (DALYs) metric.

METHODS

Epidemiological data were obtained from local databases and medical literature and were adjusted in the DisMod II tool. DALYs were obtained by adding years of life lost due to premature death (YLL) and years lived with disability (YLD).

RESULTS

The modeled prevalence of 5q-SMA in Colombia was 0.74 per 100,000 population. The fatality rate for all types was 14.1%. The disease burden of 5q-SMA was estimated at 4,421 DALYs (8.6 DALYs/100,000), corresponding to 4,214 (95.3%) YLLs and 207 (4.7%) YLDs. Most of the DALYs were accounted in the 2-17 age group. Of the total burden, 78% correspond to SMA type 1, 18% to type 2, and 4% to type 3.

CONCLUSIONS

Although 5q-SMA is a rare disease, it is linked to a significant disease burden due to premature mortality and severe sequelae. The estimates shown in this article are important inputs to inform public policy decisions on how to ensure adequate health service provision for patients with 5q-SMA.

MLPA analysis for molecular diagnosis of spinal muscular atrophy and correlation of 5q13.2 genes with disease phenotype in Egyptian patients

Background

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease representing the most prevalent monogenic cause of infant mortality. It results from the loss of SMN1 gene, but retention of its paralog SMN2 whose copy number can modulate the disease severity and guide the therapeutic regimen.

Methods

For SMA molecular analysis, 236 unrelated Egyptian patients were enrolled at our institution. The Multiplex ligation-dependent probe amplification analysis (MLPA) was applied to investigate the main genetic defect in the enrolled patients (SMN1 loss) and to determine a possible genotype–phenotype correlation between the copy number of other genes in the SMN locus (5q13.2) and disease severity in Egyptian patients with SMA. A small cohort of healthy subjects (n = 57) was also included to investigate the possible differences in the distributions of SMN2 and NAIP genes between patients and healthy individuals.

Results

Disease diagnosis was confirmed in only 148 patients (62.7%) highlighting the clinical overlapping of the disease and emphasizing the importance of molecular diagnosis. In patients with homozygous SMN1 loss, the disease was mediated by gene deletion and conversion in 135 (91.2%) and 13 (8.8%) patients, respectively. In the study cohort, SMN2 and NAIP copy numbers were inversely correlated with disease severity. However, no significant association was detected between GTF2H2A and SERF1B copy numbers and patient phenotype. Significant differences were demonstrated in the copy numbers of SMN2 and NAIP between SMA patients and healthy subjects.

Conclusion

Molecular analysis of SMA is essential for disease diagnosis. Consistent with previous studies on other populations, there is a close relationship between SMN2 and NAIP copy numbers and clinical phenotype. Additionally, potential differences in these two genes distributions are existing between patients and healthy subjects. National program for carrier screening should be established as a preventive disease strategy. On the other hand, neonatal testing would provide accurate estimation for disease incidence.

Changes in the Incidence of Infantile Spinal Muscular Atrophy in Shikoku, Japan between 2011 and 2020

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder. Al-though there was no cure for SMA, newly developed therapeutic drugs (nusinersen, onasemnogene abeparvovec, and risdiplam) have been proven effective for the improvement of motor function and prevention of respiratory insufficiency of infants with SMA. Nusinersen was introduced in Japan in 2017 and onasemnogene abeparvovec in 2020. We hypothesized that the introduction of these drugs might influence the incidence of SMA (more precisely, increase the diagnosis rate of SMA) in Japan. To test this hypothesis, we conducted a second epidemiological study of infantile SMA using questionnaires in Shikoku, Japan between October 2021 and February 2022. The incidence of infantile SMA during the period 2016-2020 was 7.08 (95% confidence interval [CI] 2.45-11.71) per 100,000 live births. According to our previous epidemiological study, the incidence of infantile SMA during 2011-2015 was 2.70 (95% CI 0.05-5.35) per 100,000 live births. The increased incidence of infantile SMA suggests that the widespread news in Japan regarding the introduction of therapeutic agents, nusinersen and onasemnogene abeparvovec, raised clinicians' awareness about SMA, leading to increased and earlier diagnosis of SMA in Shikoku.

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.

Epidemiology, healthcare resource utilization and healthcare costs for spinal muscular atrophy in Alberta, Canada

AIMS

Spinal muscular atrophy (SMA) is a progressive neuromuscular disease associated with the degeneration of motor neurons in the brainstem and spinal cord. Studies examining the epidemiology and economic impact of SMA are limited in Canada. This study aimed to estimate the epidemiology as well as healthcare resource utilization (HRU) and healthcare costs for children with SMA in Alberta, Canada.

MATERIALS AND METHODS

We conducted a retrospective study using anonymized data from administrative healthcare databases provided by Alberta Health. Data from 1 April 2010 to 31 March 2018, were extracted for patients <18 years of age identified with SMA. Five-year incidence and prevalence were calculated for cases identified between 1 April 2012 and 31 March 2017. HRU and healthcare costs were assessed one year after SMA diagnosis, including hospitalizations, physician visits, ambulatory care visits and long-term care admissions.

RESULTS

The five-year incidence and prevalence of pediatric onset SMA were 1.03 per 100,000 person-years and 9.97 per 100,000 persons, respectively. General practitioner, specialist, and ambulatory care visits were common among children with SMA in the first-year post-diagnosis. The mean (SD) total annual direct cost per patient in the first-year post-diagnosis was $29,774 ($38,407); hospitalizations accounted for 41.7% of these costs ($12,412 [$21,170]), followed by practitioner visits at 32.3% ($9,615 [$13,054]), and ambulatory care visits at 26.0% ($7,746 [$9,988]).

CONCLUSIONS

Children with SMA experience substantial HRU, particularly for hospitalizations and practitioner visits, following diagnosis. Given the high costs of SMA, timely access to effective treatment strategies, such as the novel survival motor neuron (SMN)-restoring treatments recently approved for use, are needed to improve health outcomes and HRU.

Spinal Muscular Atrophy: Diagnosis, Incidence, and Newborn Screening in Japan

Spinal muscular atrophy (SMA) is a genetic neuromuscular disorder that causes degeneration of anterior horn cells in the human spinal cord and subsequent loss of motor neurons. The severe form of SMA is among the genetic diseases with the highest infant mortality. Although SMA has been considered incurable, newly developed drugs-nusinersen and onasemnogene abeparvovec-improve the life prognoses and motor functions of affected infants. To maximize the efficacy of these drugs, treatments should be started at the pre-symptomatic stage of SMA. Thus, newborn screening for SMA is now strongly recommended. Herein, we provide some data based on our experience of SMA diagnosis by genetic testing in Japan. A total of 515 patients suspected of having SMA or another lower motor neuron disease were tested. Among these patients, 228 were diagnosed as having SMA with survival motor neuron 1 (SMN1) deletion. We analyzed the distribution of clinical subtypes and ages at genetic testing in the SMN1-deleted patients, and estimated the SMA incidence based on data from Osaka and Hyogo prefectures, Japan. Our data showed that confirmed diagnosis by genetic testing was notably delayed, and the estimated incidence was 1 in 30,000-40,000 live births, which seemed notably lower than in other countries. These findings suggest that many diagnosis-delayed or undiagnosed cases may be present in Japan. To prevent this, newborn screening programs for SMA (SMA-NBS) need to be implemented in all Japanese prefectures. In this article, we also introduce our pilot study for SMA-NBS in Osaka Prefecture.

Natural history in spinal muscular atrophy Type I in Taiwanese population: A longitudinal study

INTRODUCTION

Spinal muscular atrophy (SMA) is caused by a defect in the survival motor neuron 1 (SMN1) gene. The Cooperative Study of the natural history of SMA Type I in Taiwan is a retrospective, longitudinal, observational study that helps in further understanding SMA disease progression in patients who have not received disease-modifying therapeutic interventions.

METHODS

Case report forms were used to collect demographics; genetic confirmation; SMN2 copy number; treatment patterns; and clinical outcomes including ventilator use, endotracheal tube intubation, tracheostomy, gastrostomy, complications, and survival.

RESULTS

A total of 111 patients with SMA Type I were identified over the study period (1979-2015). Mean (median) age of onset and age at confirmed diagnosis were 1.3 (0.8) and 4.9 (4.4) months, respectively. SMN1 deletion/mutation was documented in 70 patients and SMN2 copy number in 32 (2 copies, n = 20; 3 copies, n = 12). At 240 months, survival probability for patients born during 1995-2015 versus 1979-1994 was significantly longer (p = 0.0057). Patients with 3 SMN2 copies showed substantially longer 240-month survival versus patients with 2 SMN2 copies. Over the 36-year period, mean (median) age at death was 31.9 (8.8) months. As of December 2015, 95 patients had died, 13 were alive, and 3 were lost to follow-up. The use of supportive measures (tracheostomy and gastrostomy) was associated with improved survival.

CONCLUSIONS

These data describe the short survival of patients with SMA Type I in Taiwan in the pretreatment era, emphasizing the positive impact of supportive measures on survival.

Survey of patients with spinal muscular atrophy on the island of Shikoku, Japan

BACKGROUND

Spinal muscular atrophy (SMA) is an inherited neuromuscular disorder associated with spinal motor neuron loss and characterized by generalized muscle weakness. Only a few reports exist on SMA epidemiology in Japan. Additionally, nusinersen recently became available as a treatment for this condition. We estimated the prevalence of each type of SMA on Shikoku, Japan's fourth-largest major island.

METHODS

We sent a questionnaire to all 131 hospitals in Shikoku that have pediatrics or neurology departments from March to September 2019, asking whether each hospital had SMA patients at that time. If so, we sent a second questionnaire to obtain more detailed information on the clinical data and treatment of each patient.

RESULTS

A total of 117 hospitals (89.3%) responded to our first questionnaire, and 21 SMA patients were reported, 16 of whom had homozygous deletion of SMN1. Of the 21, nine had SMA type 1, five were type 2, five were type 3, one was type 4, and one was unidentified. The estimated prevalence for all instances of SMA and 5q-SMA was 0.56 and 0.43 per 100,000 people, respectively. Thirteen patients had received nusinersen therapy. Its outcomes varied from no obvious effects and being unable to sit to being able to sit independently.

CONCLUSION

Our data showed the prevalence of SMA types 2 and 3 was relatively low on Shikoku compared with previous reports from other countries, suggesting delayed diagnosis may affect the results. Remaining motor function may be one predicting factor. Greater awareness of SMA among clinicians and patients seems necessary for more accurate epidemiological studies.