Genetic profile of Brazilian patients with LAMA2-related dystrophies.

LAMA2-related dystrophies (LAMA2-RD) constitute a rare neuromuscular disorder with a broad spectrum of phenotypic severity. Our understanding of the genotype-phenotype correlations in this condition remains incomplete, and reliable clinical data for clinical trial readiness is limited. In this retrospective study, we reviewed the genetic data and medical records of 114 LAMA2-RD patients enrolled at seven research centers in Brazil. We identified 58 different pathogenic variants, including 21 novel ones. Six variants were more prevalent and were present in 81.5% of the patients. Notably, the c.1255del, c.2049_2050del, c.3976 C>T, c.5234+1G>A, and c.4739dup variants were found in patients unable to walk and without cortical malformation. In contrast, the c.2461A>C variant was present in patients who could walk unassisted. Among ambulatory patients, missense variants were more prevalent (p < 0.0001). Although no specific hotspot regions existed in the LAMA2, 51% of point mutations were in the LN domain, and 88% of the missense variants were found within this domain. Functional analysis was performed in one intronic variant (c.4960-17C>A) and revealed an out-of-frame transcript, indicating that the variant creates a cryptic splicing site (AG). Our study has shed light on crucial phenotype-genotype correlations and provided valuable insights, particularly regarding the Latin American population.

Clinical and molecular characterization of limb-girdle muscular dystrophy 2G/R7 in a large cohort of Brazilian patients.

Limb-girdle muscular dystrophy type 2G/R7 (LGMD2G/R7) is an ultra-rare condition initially identified within the Brazilian population. We aimed to expand clinical and genetic information about this disease, including its worldwide distribution. A multicenter historical cohort study was performed at 13 centers in Brazil in which data from index cases and their affected relatives from consecutive families with LGMD2G/R7 were reviewed from July 2017 to August 2023. Additionally, a systematic literature review was conducted to identify case reports and series of the disease worldwide. Forty-one LGMD2G/R7 cases were described in the Brazilian cohort, being all subjects homozygous for the c.157C>T/(p.Gln53*) variant in TCAP. Survival curves showed that the median disease duration before individuals required walking aids was 21 years. Notably, women exhibited a slower disease progression, requiring walking aids 13 years later than men. LGMD2G/R7 was frequently reported not only in Brazil but also in China and Bulgaria, with 119 cases identified globally, with possible founder effects in the Brazilian, Eastern European, and Asian populations. These findings are pivotal in raising awareness of LGMD2G/R7, understanding its progression, and identifying potential modifiers. This can significantly contribute to the development of future natural history studies and clinical trials for this disease.

Static Balance in Hereditary Spastic Paraplegias: a Cross-sectional Study.

Motor and somatosensory pathway dysfunction due to degeneration of long tracts in hereditary spastic paraplegias (HSP) indicates that postural abnormalities may be a relevant disease feature. However, balance assessments have been underutilized to study these conditions. How does the static balance of individuals with HSP with eyes open and closed differ from healthy controls, and how does it relate to disease severity? This cross-sectional case-control study assessed the static balance of 17 subjects with genetically confirmed HSP and 17 healthy individuals, evaluating the center of pressure (COP) variables captured by a force platform. The root-mean-square of velocities and mean of displacements amplitudes in mediolateral and anteroposterior axes were correlated with disease severity. All COP parameters' performances were significantly impaired in HSP subjects compared to controls (p < 0.001 for all comparisons). COP with eyes open and closed differed for all variables within the HSP group, whereas in the control group, differences were observed only for anteroposterior velocity and amplitude. Spastic Paraplegia Rating Scale presented moderate direct correlations with the most COP variables (Rho = - 0.520 to - 0.736). HSP individuals presented significant postural instability with eyes open and to a greater extent with eyes closed, corroborating the clinical findings of somatosensorial and proprioceptive pathways dysfunction. The degrees of proprioceptive and motor impairments are mutually correlated, suggesting that similar pathophysiological mechanisms operate for the degeneration of these long tracts. COP parameters can be seen as disease severity biomarkers of HSP, and they should be assessed in future clinical trials.

Postural adjustments and perceptual responses of Nordic running: concurrent effects of poles and irregular terrain.

PURPOSE: In the natural environment, humans must continuously negotiate irregular and unpredictable terrain. Recently, the poles have been extensively used during trial running events. However, we know little about how humans adjust posture and bilateral coordination to use poles in irregular terrain. Here, we compared kinematics, bilateral coordination and perceptual responses between regular (compact dust) and irregular terrain (medium-length grass) during running at preferred speed with and without poles. METHODS: In this transversal observational study, thirteen young healthy adults (8 men; mean ± SD; age 29.1 ± 8.0 years, body mass 76.8 ± 11.4 kg; height 1.75 ± 0.08 m) were evaluated during running at a self-selected comfortable speed with and without poles on regular and irregular terrains. RESULTS: Our results show that, despite more flexed pattern on lower-limb joints at irregular terrain, the usage of poles was not enough to re-stabilize the bilateral coordination. Also, the perceived exertion was impaired adding poles to running, probably due to more complex movement pattern using poles in comparison to free running, and the invariance in the bilateral coordination. CONCLUSION: Besides the invariability of usage poles on bilateral coordination and lower-limb kinematics, the runners seem to prioritize postural stability over lower limb stiffness when running in medium-length grass given the larger range of ankle and knee motion observed in irregular terrain. Further investigations at rougher/hilly terrains will likely provide additional insights into the neuromotor control strategies used to maintain the stability and on perceptual responses using poles during running.

Copy number variations in SPAST and ATL1 are rare among Brazilians.

Copy number variations (CNV) may represent a significant proportion of SPG4 and SPG3A diagnosis, the most frequent autosomal dominant subtypes of hereditary spastic paraplegias (HSP). We aimed to assess the frequency of CNVs in SPAST and ATL1 and to update the molecular epidemiology of HSP families in southern Brazil. A cohort study that included 95 Brazilian index cases with clinical suspicion of HSP was conducted between April 2011 and September 2022. Multiplex Ligation Dependent Probe Amplification (MLPA) was performed in 41 cases without defined diagnosis by different massive parallel sequencing techniques (MPS). Diagnosis was obtained in 57/95 (60%) index cases, 15/57 (26.3%) being SPG4. Most frequent autosomal recessive HSP subtypes were SPG7 followed by SPG11, SPG76 and cerebrotendinous xanthomatosis. No CNVs in SPAST and ATL1 were found. Copy number variations are rare among SPG4 and SPG3A families in Brazil. Considering the possibility of CNVs detection by specific algorithms with MPS data, we consider that this is likely the most cost-effective approach to investigate CNVs in these genes in low-risk populations, with MLPA being reserved as an orthogonal confirmatory test.

Neonatal screening for spinal muscular atrophy: A pilot study in Brazil.

Spinal muscular atrophy (SMA) is considered one of the most common autosomal recessive disorders, with an estimated incidence of 1 in 10,000 live births. Testing for SMA has been recommended for inclusion in neonatal screening (NBS) panels since there are several therapies available and there is evidence of greater efficacy when introduced in the pre/early symptomatic phases. In Brazil, the National Neonatal Screening Program tests for six diseases, with a new law issued in 2021 stating that it should incorporate more diseases, including SMA. In the present study, dried blood spot (DBS) samples collected by the Reference Services of Neonatal Screening of RS and SP, to perform the conventional test were also screened for SMA, using real-time PCR, with SALSA MC002 technique. A total of 40,000 samples were analyzed, enabling the identification of four positive cases of SMA, that were confirmed by MLPA. Considering our sampling, Brazil seems to have an incidence comparable to the described in other regions. This work demonstrated that the use of the MC002 technique in samples routinely collected for the conventional NBS program is suitable to screen for SMA in our conditions and can be included in the expansion of the neonatal screening programs.

Progression of Functional Gait in Hereditary Spastic Paraplegias.

Hereditary spastic paraplegias (HSP) are characterized by progressive deterioration of axonal projections of upper motor neurons leading to abnormal locomotion. The clinical course of HSP as well as the definition of the best instruments to assess its progression is largely unknown. The aim of this study was to investigate the progression of functional gait in individuals with HSP and to define sensitivity to change, minimal clinically important difference (MCID), and validity of timed functional tests of gait (TFT). The study was constituted of two phases: a cross-sectional study and a prospective cohort of 18 months. Twenty-five patients (17 being SPG4), and twenty-five age- and sex-matched control individuals performed TFT. Spastic paraplegia rating scale (SPRS), ten-meter walking test (10MWT), timed up and go test (TUG), both at self-selected and maximal walking speeds, and six-minute walking test (6MWT) were performed on baseline in both groups and after 18 months of follow-up only in the HSP cohort. In the cross-sectional analysis, all TFTs performances were greatly impaired in HSP patients compared to controls. After 18 months of follow-up, TFTs did not differ significantly from baseline in the statistical analysis, with some tests showing more frequent improvement than worsening. We have provided effect size measures and MCID for the evaluated instruments. HSPs clearly compromised TFTs performances, which were valid instruments for assessing disease severity. However, TFTs and SPRS did not capture the very slow motor evolution of HSPs, reinforcing the necessity of additional biomarkers of disease progression.

Diagnostic yield of multi-gene panel for muscular dystrophies and other hereditary myopathies.

Genetic testing is being considered the first-step in the investigation of hereditary myopathies. However, the performance of the different testing approaches is little known. The aims of the present study were to evaluate the diagnostic yield of a next-generation sequencing panel comprising 39 genes as the first-tier test for genetic myopathies diagnosis and to characterize clinical and molecular findings of families from southern Brazil. Fifty-one consecutive index cases with clinical suspicion of genetic myopathies were recruited from October 2014 to March 2018 in a cross-sectional study. The overall diagnostic yield of the next-generation sequencing panel was 52.9%, increasing to 60.8% when including cases with candidate variants. Multi-gene panel solved the diagnosis of 12/25 (48%) probands with limb-girdle muscular dystrophies, of 7/14 (50%) with congenital muscular diseases, and of 7/10 (70%) with muscular dystrophy with prominent joint contractures. The most frequent diagnosis for limb-girdle muscular dystrophies were LGMD2A/LGMD-R1-calpain3-related and LGMD2B/LGMD-R2-dysferlin-related; for congenital muscular diseases, RYR1-related-disorders; and for muscular dystrophy with prominent joint contractures, Emery-Dreifuss-muscular-dystrophy-type-1 and COL6A1-related-disorders. In summary, the customized next-generation sequencing panel when applied in the initial investigation of genetic myopathies results in high diagnostic yield, likely reducing patient's diagnostic odyssey and providing important information for genetic counseling and participation in disease-specific clinical trials.

Clinical trials for genetic diseases in Latin America.

Latin American geneticists have been contributing to the scientific development of Human and Medical Genetics fields since the early 1950s. In the last decades, as Medical Genetics is moving toward a new era of innovative therapies for previously untreatable conditions, the participation of Latin America in clinical trials is also increasing. This review discusses the particularities regarding funding, regulatory, and ethical aspects of conducting clinical trials for genetic diseases in Latin America, with an especial focus on Brazil, the largest country with the highest number of studies. Although there are still several barriers to overcome, the recent development of orphan drug legislation and policies for rare diseases in many Latin American countries indicates a growing opportunity for the participation of the region in international efforts for the development of new therapies for genetic diseases.

Diagnostic yield of targeted sequential and massive panel approaches for inherited neuropathies.

Diagnostic yield of genetic studies for Charcot-Marie-Tooth disease (CMT) is little known, with a lack of epidemiological data to build better diagnostic strategies outside the United States and Europe. We aimed to evaluate the performance of two molecular diagnostic strategies for patients with CMT, and to characterize epidemiological findings of these conditions in southern Brazil. We performed a single-center cross-sectional study, in which 94 patients (55 families) with CMT suspicion were evaluated. Overall, the diagnostic yield of the combined strategy of Multiplex-ligation-dependent-probe-amplification (MLPA) of PMP22/GJB1/MPZ and GJB1/MPZ/PMP22 Sanger sequencing was 63.6% (28/44) for index cases with demyelinating/intermediate CMT suspicion (21 CMT1A-PMP22, 5 CMTX1-GJB1 and 2 with probably CMT1B-MPZ diagnosis). Five of the 11 index cases (45.4%) with axonal CMT had at least a possible diagnosis with next generation sequencing (NGS) panel of 104 inherited neuropathies-related genes (one each with CMT1A-PMP22, CMT2A-MFN2, CMT2K-GDAP1, CMT2U-MARS, CMT2W-HARS1). Detailed clinical, neurophysiological and molecular data of families are provided. Sequential molecular diagnosis strategies with MLPA plus target Sanger sequencing for demyelinating/intermediate CMT had high diagnostic yield, and almost half of axonal CMT families had at least a possible diagnosis with the comprehensive NGS panel. Most frequent subtypes of CMT in our region are CMT1A-PMP22 and CMTX1-GJB1.

A systematic review and evidence-based guideline for diagnosis and treatment of Menkes disease.

Menkes disease is a rare X-linked neurodegenerative disorder caused by defect in copper metabolism. Parenteral copper supplementation has been used as a potential disease-modifying treatment of Menkes disease for decades. However, recent evidence suggests its efficacy only when treatment is started within days after birth, which also has important implications related to the techniques that enable early diagnosis. We aim at proposing a guideline for prenatal and neonatal diagnosis and for disease-modifying treatment of Menkes disease, guided by a systematic review of the literature, and built in conjunction with medical experts, methodologists and patient representatives. Thirteen articles were used for our recommendations that were based on GRADE system. Reviewed evidence suggests that prenatal genetic diagnosis in families with previous diagnosis of Menkes disease is feasible; analysis of plasma catecholamine levels is accurate for neonatal diagnosis of Menkes disease; treatment with copper-histidine is effective to increase survival and reduce neurologic burden of the disease if initiated in the neonatal period; and, treatment indication should not be guided by patient's genotype. In conclusion, our guideline can contribute to standardize some aspects of the clinical care of patients with Menkes disease, especially reducing disease burden and mortality and providers' and families' anxiety.

State biomarkers for Machado Joseph disease: Validation, feasibility and responsiveness to change.

Machado-Joseph disease (SCA3/MJD) is the most common spinocerebellar ataxia worldwide, and particularly so in Southern Brazil. Due to an expanded polyglutamine at ataxin-3, SCA3/MJD presents a relentless course with no current disease modifying treatment. Clinical scales used to measure SCA3/MJD progression present moderate effect sizes, a major drawback for their use as main outcomes in clinical trials, given the rarity and slow progression of the disease. This limitation might be overcome by finding good surrogate markers. We present here a review of studies on peripheral and neurophysiological markers in SCA3/MJD that can be candidates for state biomarkers. Data on markers already studied were summarized, giving emphasis on validation against clinical scale, and responsiveness to change. While some biological fluid compounds and neurophysiological parameters showed poor responsiveness, others seemed to be good candidates. Some potential candidates that are waiting for responsiveness studies were serum levels of neuron specific enolase, vestibulo-ocular reflex and video-oculography. Candidates evaluated by RNA and microRNA expression levels need further studies to improve their measurements. Data on peripheral levels of Beclin-1 and DNAJB1 are promising but still incipient. We conclude that several potential candidates should follow onto validating studies for surrogate state biomarkers of SCA3/MJD.

Planning Future Clinical Trials for Machado-Joseph Disease.

Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) is an autosomal dominant multiple neurological systems degenerative disorder caused by a CAG repeat expansion at ATXN3 gene. Only a few treatments were evaluated in randomized clinical trials (RCT) in SCA3/MJD patients, with a lack of evidence for both disease-modifying and symptomatic therapies. The present chapter discuss in detail major methodological issues for planning future RCT for SCA3/MJD. There are several potential therapies for SCA3/MJD with encouraging preclinical results. Route of treatment, dosage titration and potential therapy biomarkers might differ among candidate drugs; however, the core study design and protocol will be mostly the same. RCT against placebo group is the best study design to test a disease-modifying therapy; the same cannot be stated for some symptomatic treatments. Main outcomes for future RCT are clinical scales: the Scale for the Assessment and Rating of ataxia (SARA) is currently the instrument of choice to prove efficacy of disease-modifying or symptomatic treatments against ataxia, the most important disease feature. Ataxia quantitative scales or its composite scores can be used as primary outcomes to provide preliminary evidence of efficacy in phase 2 RCT, due to a greater sensitivity to change. Details regarding eligibility criteria, randomization, sample size estimation, duration and type of analysis for both disease modifying and symptomatic treatment trials, were also discussed. Finally, a section anticipates the methodological issues for testing novel drugs when an effective treatment is already available. We conclude emphasizing four points, the first being the need of RCT for a number of different aims in the care of SCA3/MJD. Due to large sample sizes needed to warrant power, RCT for disease-modifying therapies should be multicenter enterprises. There is an urge need for surrogate markers validated for several drug classes. Finally, engagement of at risk or presymptomatic individuals in future trials will enable major advances on treatment research for SCA3/MJD.

Spinocerebellar ataxia type 3/Machado-Joseph disease starting before adolescence.

Onset of Machado-Joseph disease (SCA3/MJD) before adolescence has been rarely reported. This study aims to describe a cohort of SCA3/MJD with onset before 12 years of age, comparing their disease progression with the progression observed in patients with usual disease onset. We identified all cases from our cohort whose onset was before adolescence. After consent, patients were examined with clinical scales Scale for the Assessment and Rating of Ataxia (SARA) and Neurological Examination Score for Spinocerebellar Ataxia (NESSCA). Gender, age, age at onset, disease duration, CAG expanded repeats, transmitting parent, and anticipation of cases with infantile and adult onset were studied. Progression of NESSCA and SARA scores was estimated through a mixed model, and was compared with a historical group with onset after adolescence. Between 2000 and 2014, 461 symptomatic individuals from our region were diagnosed as SCA3/MJD. Onset of eight cases (2.2%), all heterozygotes, was before adolescence: seven were females (p = 0.054). CAG expanded repeats--75 ± 3 versus 84 ± 4--and anticipations--7 ± 9.7 versus 14.4 ± 7.2 years--were different between early childhood and adult onset groups (p < 0.03). The median survival of early childhood onset group was 23 years of age. The annual progression of SARA--2.3 and 0.6 points/year (p = 0.001)--and NESSCA--2.04 and 0.88 points/year (p = 0.043)--was faster in childhood than in adult onset group. Onset of SCA3/MJD before adolescence was related to larger expanded CAG repeats in heterozygosis; females seemed to be at higher risk. Disease progression was faster than in SCA3/MJD starting after 12 years.

Cytokines in Machado Joseph Disease/Spinocerebellar Ataxia 3.

The aim of the present study is to describe the serum concentrations of a broad spectrum of cytokines in symptomatic and asymptomatic carriers of Machado Joseph disease (SCA3/MJD) CAG expansions. Molecularly confirmed carriers and controls were studied. Age at onset, disease duration, and clinical scales Scale for the Assessment and Rating of Ataxia (SARA), Neurological Examination Score for Spinocerebellar Ataxias (NESSCA), SCA Functional Index (SCAFI), and Composite Cerebellar Functional Score (CCFS) were obtained from the symptomatic carriers. Serum was obtained from all individuals and a cytokine panel "consisted of" eotaxin, granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon (IFN)-α, IFN-γ, interleukin (IL)-1ß, IL-1RA, IL-2, IL-2R, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-15, IL-17, interferon gamma-induced protein (IP)-10, monocyte chemoattractant protein (MCP)-1, monokine induced by gamma interferon (MIG), macrophage inflammatory protein (MIP)-a, MIP-b, regulated on activation, normal T cell expressed and secreted (RANTES) and tumor necrosis factor (TNF)-α was analyzed. In a subgroup of symptomatic carriers, the cytokine panel was repeated after 360 days. Cytokine distribution among groups was studied by discriminant analysis; changes in serum levels after 360 days were studied by generalized estimation equation. Sixty-six symptomatic carriers, 13 asymptomatic carriers, and 43 controls were studied. No differences in cytokine patterns were found between controls and carriers of the CAG expansions or between controls and symptomatic carriers only. In contrast, eotaxin concentrations were significantly higher in asymptomatic than in symptomatic carriers or in controls (p = 0.001, ANCOVA). Eotaxin did not correlate with age, disease duration, CAG expansion, NESSCA score, and SARA score. Among symptomatic carriers, eotaxin dropped after 360 days (p = 0.039, GEE). SCA3/MJD patients presented a benign pattern of serum cytokines. In contrast, levels of eotaxin, a peptide secreted by astrocytes, were elevated in the asymptomatic carriers, suggesting that a specific response of these cells can be related to symptom progression, in SCA3/MJD.

A randomized, phase 2 clinical trial of lithium carbonate in Machado-Joseph disease.

BACKGROUND: Because lithium exerts neuroprotective effects in preclinical models of polyglutamine disorders, our objective was to assess the safety and efficacy of lithium carbonate (0.5-0.8 milliequivalents per liter) in patients with Machado-Joseph disease (spinocerebellar ataxia type 3 [MJD/SCA3]). METHODS: For this phase 2, single-center, double-blind, parallel, placebo-controlled trial (ClinicalTrials.gov identifier NCT01096082), 62 patients who had MJD/SCA3 with a disease duration ≤10 years and an independent gait were randomly assigned (1:1) to receive either lithium or placebo. RESULTS: After 24 weeks, 169 adverse events were reported, including 50.3% in the lithium group (P = 1.00; primary safety outcome). Sixty patients (31 in the placebo group and 29 in the lithium group) were analyzed for efficacy (intention-to-treat analysis). Mean progression between groups did not differ according to scores on the Neurological Examination Score for the Assessment of Spinocerebellar Ataxia (NESSCA) after 48 weeks (-0.35; 95% confidence interval, -1.7 to 1.0; primary efficacy outcome). The lithium group exhibited minor progression on the PATA speech-rate (P = 0.002), the nondominant Click Test (P = 0.023), the Spinocerebellar Ataxia Functional Index (P = 0.003), and the Composite Cerebellar Functional Score (P = 0.029). CONCLUSIONS: Lithium was safe and well tolerated, but it had no effect on progression when measured using the NESSCA in patients with MJD/SCA3. This slowdown in secondary outcomes deserves further clarification.

Empowerment of genetic information by women at-risk of being carriers of Duchenne and Becker muscular dystrophies.

The emergence of therapies acting on specific molecular targets for Duchenne and Becker muscular dystrophies (DBMD) led to expanded access of diagnostic DMD analysis. However, it is unclear how much of these advances have also improved healthcare and access to genetic testing for women at-risk of being carriers. This study evaluates the process of genetic counseling and empowerment of genetic information by women from DBMD families. We carried out a cross-sectional study between February and June 2022 in Brazil. The online survey with items regarding sociodemographic data; family history; access to health services; reproductive decisions; and the Genomic Outcome Scale was answered by 123 women recruited from a rare diseases reference service and a nationwide patient advocacy group. Genetic counseling was reported by 77/123 (62.6%) of women and 53.7% reported having performed genetic analysis of DMD. Although the majority knew about the risks for carriers of developing heart disease and muscle weakness, only 35% of potential carriers have had cardiac studies performed at least once in their lives. Country region, type of kinship, number of affected males in the family, age, notion of genetic risk, education level, and participation in advocacy groups were the main factors associated with adequate healthcare access to women and empowerment of genetic information. Education to health professionals and policies to expand access to carrier genetic testing, whether public policies or regulation of pharmaceutical companies' diagnostic programs, is paramount to improve the care of families with DBMD in Brazil.

Co-Occurrence of Myotonic Dystrophy Type 1 and Limb-Girdle Muscular Dystrophy Type 2B: A Case Report.

Introduction: Myotonic dystrophy type 1 (DM1) is an autosomal dominant neuromuscular disease whose pattern of weakness is predominantly distal. Limb-girdle muscular dystrophy type 2B/R2-dysferlin-related (LGMD2B/R2) is another neuromuscular disease, which presents an autosomal recessive inheritance and is marked by proximal muscle weakness. Even if uncommon, comorbid inherited pathologies must be considered in cases of atypical presentations, especially in those with family history of consanguinity. Case Presentation: Herein, we report the unique case of a patient diagnosed with both DM1 and LGMD2B/R2: a 38-year-old woman in follow-up of DM1 in a neuromuscular disease service presenting prominent proximal weakness. The patient's parents were consanguineous, and creatine kinase levels were elevated. A multi-gene panel test was performed and revealed the diagnosis of LGMD2B/R2. Conclusion: Genetic diseases with atypical presentations should raise the possibility of a second disorder, prompting an appropriate investigation. Overlooking a second diagnosis can implicate in not offering adequate genetic counseling, support, or specific treatment.

Serum myostatin as a candidate disease severity and progression biomarker of spinal muscular atrophy.

The identification of biomarkers for spinal muscular atrophy is crucial for predicting disease progression, severity, and response to new disease-modifying therapies. This study aimed to investigate the role of serum levels of myostatin and follistatin as biomarkers for spinal muscular atrophy, considering muscle atrophy secondary to denervation as the main clinical manifestation of the disease. The study evaluated the differential gene expression of myostatin and follistatin in a lesional model of gastrocnemius denervation in mice, as well as in a meta-analysis of three datasets in transgenic mice models of spinal muscular atrophy, and in two studies involving humans with spinal muscular atrophy. Subsequently, a case-control study involving 27 spinal muscular atrophy patients and 27 controls was conducted, followed by a 12-month cohort study with 25 spinal muscular atrophy cases. Serum levels of myostatin and follistatin were analysed using enzyme-linked immunosorbent assay at a single centre in southern Brazil. Skeletal muscle gene expression of myostatin decreased and of follistatin increased following lesional muscle denervation in mice, consistent with findings in the spinal muscular atrophy transgenic mice meta-analysis and in the iliopsoas muscle of five patients with spinal muscular atrophy type 1. Median serum myostatin levels were significantly lower in spinal muscular atrophy patients (98 pg/mL; 5-157) compared to controls (412 pg/mL; 299-730) (P < 0.001). Lower myostatin levels were associated with greater disease severity based on clinician-rated outcomes (Rho = 0.493-0.812; P < 0.05). After 12 months, there was a further reduction in myostatin levels among spinal muscular atrophy cases (P = 0.021). Follistatin levels did not differ between cases and controls, and no significant changes were observed over time. The follistatin:myostatin ratio was significantly increased in spinal muscular atrophy subjects and inversely correlated with motor severity. Serum myostatin levels show promise as a novel biomarker for evaluating the severity and progression of spinal muscular atrophy. The decrease in myostatin levels and the subsequent favourable environment for muscle growth may be attributed to denervation caused by motor neuron dysfunction.