Genome and RNA sequencing boost neuromuscular diagnoses to 62% from 34% with exome sequencing alone.

OBJECTIVE: Most families with heritable neuromuscular disorders do not receive a molecular diagnosis. Here we evaluate diagnostic utility of exome, genome, RNA sequencing, and protein studies and provide evidence-based recommendations for their integration into practice. METHODS: In total, 247 families with suspected monogenic neuromuscular disorders who remained without a genetic diagnosis after standard diagnostic investigations underwent research-led massively parallel sequencing: neuromuscular disorder gene panel, exome, genome, and/or RNA sequencing to identify causal variants. Protein and RNA studies were also deployed when required. RESULTS: Integration of exome sequencing and auxiliary genome, RNA and/or protein studies identified causal or likely causal variants in 62% (152 out of 247) of families. Exome sequencing alone informed 55% (83 out of 152) of diagnoses, with remaining diagnoses (45%; 69 out of 152) requiring genome sequencing, RNA and/or protein studies to identify variants and/or support pathogenicity. Arrestingly, novel disease genes accounted for <4% (6 out of 152) of diagnoses while 36.2% of solved families (55 out of 152) harbored at least one splice-altering or structural variant in a known neuromuscular disorder gene. We posit that contemporary neuromuscular disorder gene-panel sequencing could likely provide 66% (100 out of 152) of our diagnoses today. INTERPRETATION: Our results emphasize thorough clinical phenotyping to enable deep scrutiny of all rare genetic variation in phenotypically consistent genes. Post-exome auxiliary investigations extended our diagnostic yield by 81% overall (34-62%). We present a diagnostic algorithm that details deployment of genomic and auxiliary investigations to obtain these diagnoses today most effectively. We hope this provides a practical guide for clinicians as they gain greater access to clinical genome and transcriptome sequencing.

Facioscapulohumeral muscular dystrophy type 2: an update on the clinical, genetic, and molecular findings.

Facioscapulohumeral muscular dystrophy (FSHD) is a common genetic disease of the skeletal muscle with a characteristic pattern of weakness. Facioscapulohumeral muscular dystrophy type 2 (FSHD2) accounts for approximately 5% of all cases of FSHD and describes patients without a D4Z4 repeat contraction on chromosome 4. Phenotypically FSHD2 shows virtually no difference from FSHD1 and both forms of FSHD arise via a common downstream mechanism of epigenetic derepression of the transcription factor DUX4 in skeletal muscle cells. This results in expression of DUX4 and target genes leading to skeletal muscle toxicity. Over the past decade, major progress has been made in our understanding of the genetic and epigenetic architecture that underlies FSHD2 pathogenesis, as well as the clinical manifestations and disease progression. These include the finding that FSHD2 is a digenic disease and that mutations in the genes SMCHD1, DNMT3B, and more recently LRIF1, can cause FSHD2. FSHD2 is complex and it is important that clinicians keep abreast of recent developments; this review aims to serve as an update of the clinical, genetic, and molecular research into this condition.

The facioscapulohumeral muscular dystrophy Rasch-built overall disability scale (FSHD-RODS).

BACKGROUND AND OBJECTIVES: Facioscapulohumeral muscular dystrophy (FHSD) is a debilitating inherited muscle disease for which various therapeutic strategies are being investigated. Thus far, little attention has been given in FSHD to the development of scientifically sound outcome measures fulfilling regulatory authority requirements. The aim of this study was to design a patient-reported Rasch-built interval scale on activity and participation for FSHD. METHODS: A pre-phase FSHD-Rasch-built overall disability scale (pre-FSHD-RODS; consisting of 159 activity/participation items), based on the World Health Organization international classification of disease-related functional consequences was completed by 762 FSHD patients (Netherlands: n = 171; UK: n = 287; United States: n = 221; France: n = 52; Australia: n = 32). A proportion of the patient cohort completed it twice (n = 230; interval 2-4 weeks; reliability studies). The pre-FSHD-RODS was subjected to Rasch analyses to create a model fulfilling its requirements. Validity studies were performed through correlation with the motor function measure. RESULTS: The pre-FSHD-RODS did not meet the Rasch model expectations. Based on determinants such as misfit statistics and misfit residuals, differential item functioning, and local dependency, we systematically removed items until a final 38-inquiry (originating from 32 items; six items split) FSHD-RODS was constructed achieving Rasch model expectations. Adequate test-retest reliability and (cross-cultural and external) validity scores were obtained. CONCLUSIONS: The FSHD-RODS is a disease-specific interval measure suitable for detecting activity and participation restrictions in patients with FSHD with good item/person reliability and validity scores. The use of this scale is recommended in the near future, to determine the functional deterioration slope in FSHD per year as a preparation for the upcoming clinical intervention trials in FSHD.

Is it Pompe Disease? Australian diagnostic considerations.

Pompe Disease is a spectrum disorder with an evolving phenotype in which diagnostic delay is common. Contributing factors include the rarity of the disorder, its wide clinical spectrum, signs and symptoms that overlap with those of other neuromuscular disorders, variable diagnostic approaches, lack of awareness of the clinical manifestations and difficulties in completing the diagnostic inventory. International updates and recommendations have been published providing diagnostic guidelines and management criteria. However, questions remain in the Australian setting. A panel (two neurologists, one clinical geneticist) reviewed the literature, examined clinical questions of relevance to the Australian setting, and developed a framework for the guidance. A wider panel, comprising the initial panel plus eight additional members, critiqued the framework and contributed clinical guidance within the scope of their respective areas of clinical expertise. The resultant expert consensus recommendations build on currently available data to propose an appropriate management framework incorporating the diagnosis, classification, therapeutic approach, multidisciplinary care, and on-going monitoring of patients with Pompe Disease in the Australian setting. It is hoped that diagnostic delay can be reduced with appropriate recourse to evidence-based insights and practical advice on diagnosis and management tailored to the Australian setting.

Enhanced serum immunoglobulin G clearance in myotonic dystrophy-associated hypogammaglobulinemia: a case series and review of the literature.

BACKGROUND: Myotonic dystrophy type 1 is an autosomal dominant disorder characterized by muscle weakness, myotonia, cataracts, and cardiac conduction defects; it is associated with expansions of cytosine-thymine-guanine repeats in the myotonic dystrophy protein kinase. Hypogammaglobulinemia is a lesser known association of myotonic dystrophy type 1 and the underlying pathogenesis of immunoglobulin G depletion remains unclear. CASE PRESENTATION: Here we report a kindred of two members (a 62-year-old white woman and a 30-year-old white man; mother and son) with myotonic dystrophy type 1-associated hypogammaglobulinemia associated with altered intravenous immunoglobulin elimination kinetics and reduced half-life. There was no history of systemic immunosuppression or renal or gastrointestinal protein loss in either patient, and no underlying case for a secondary immunodeficiency could be found. One patient required fortnightly intravenous immunoglobulin to maintain adequate trough immunoglobulin G levels. CONCLUSIONS: Ongoing study of myotonic dystrophy type 1-associated hypogammaglobulinemia using contemporary tools of genomic medicine may help to further delineate the pathogenesis of this entity.

Recessive DES cardio/myopathy without myofibrillar aggregates: intronic splice variant silences one allele leaving only missense L190P-desmin.

We establish autosomal recessive DES variants p.(Leu190Pro) and a deep intronic splice variant causing inclusion of a frameshift-inducing artificial exon/intronic fragment, as the likely cause of myopathy with cardiac involvement in female siblings. Both sisters presented in their twenties with slowly progressive limb girdle weakness, severe systolic dysfunction, and progressive, severe respiratory weakness. Desmin is an intermediate filament protein typically associated with autosomal dominant myofibrillar myopathy with cardiac involvement. However a few rare cases of autosomal recessive desminopathy are reported. In this family, a paternal missense p.(Leu190Pro) variant was viewed unlikely to be causative of autosomal dominant desminopathy, as the father and brothers carrying this variant were clinically unaffected. Clinical fit with a DES-related myopathy encouraged closer scrutiny of all DES variants, identifying a maternal deep intronic variant within intron-7, predicted to create a cryptic splice site, which segregated with disease. RNA sequencing and studies of muscle cDNA confirmed the deep intronic variant caused aberrant splicing of an artificial exon/intronic fragment into maternal DES mRNA transcripts, encoding a premature termination codon, and potently activating nonsense-mediate decay (92% paternal DES transcripts, 8% maternal). Western blot showed 60-75% reduction in desmin levels, likely comprised only of missense p.(Leu190Pro) desmin. Biopsy showed fibre size variation with increased central nuclei. Electron microscopy showed extensive myofibrillar disarray, duplication of the basal lamina, but no inclusions or aggregates. This study expands the phenotypic spectrum of recessive DES cardio/myopathy, and emphasizes the continuing importance of muscle biopsy for functional genomics pursuit of 'tricky' variants in neuromuscular conditions.

High Degree of Genetic Heterogeneity for Hereditary Cerebellar Ataxias in Australia.

Genetic testing strategies such as next-generation sequencing (NGS) panels and whole genome sequencing (WGS) can be applied to the hereditary cerebellar ataxias (HCAs), but their exact role in the diagnostic pathway is unclear. We aim to determine the yield from genetic testing strategies and the genetic and phenotypic spectrum of HCA in Australia by analysing real-world data. We performed a retrospective review on 87 HCA cases referred to the Neurogenetics Clinic at the Royal North Shore Hospital, Sydney, Australia. Probands underwent triplet repeat expansion testing; those that tested negative had NGS-targeted panels and WGS testing when available. In our sample, 58.6% were male (51/87), with an average age at onset of 37.1 years. Individuals with sequencing variants had a prolonged duration of illness compared to those with a triplet repeat expansion. The detection rate in probands for routine repeat expansion panels was 13.8% (11/80). NGS-targeted panels yielded a further 11 individuals (11/32, 34.4%), with WGS yielding 1 more diagnosis (1/3, 33.3%). NGS panels and WGS improved the overall diagnostic rate to 28.8% (23/80) in 14 known HCA loci. The genetic findings included novel variants in ANO10, CACNA1A, PRKCG and SPG7. Our findings highlight the genetic heterogeneity of HCAs and support the use of NGS approaches for individuals who were negative on repeat expansion testing. In comparison to repeat disorders, individuals with sequencing variants may have a prolonged duration of illness, consistent with slower progression of disease.

Warts and all: Fingolimod and unusual HPV-associated lesions.

BACKGROUND: Fingolimod is used to reduce relapse rates in relapsing-remitting multiple sclerosis (MS). It is a sphingosine 1-phosphate (S1P) analogue having antagonistic effects on S1P receptors. Its immunosuppressive effect is due to reduced circulating lymphocyte numbers, and it may also be associated with impaired intrinsic cancer surveillance. Fingolimod side effects include increased rates and severity of viral infections particularly varicella zoster. METHODS: We present five cases of chronic and treatment refractory warts associated with fingolimod therapy. RESULTS: Each of the five cases presenting with chronic warts while receiving fingolimod therapy had prolonged periods of lymphopenia and improvements were seen following dose reduction or cessation of fingolimod. CONCLUSION: Cutaneous warts are associated with human papilloma virus (HPV) infection, suggesting an increased risk of other HPV-driven conditions such as cervical cancer following fingolimod administration. HPV viruses are responsible for approximately 90% of cervical cancers as well as a significant portion of anogenital cancers and have a high prevalence in sexually active adults. Given the reduced immune response to viral infections and potential impaired cancer surveillance in those receiving fingolimod, HPV vaccination and frequent assessment for the development of HPV-associated malignancies are recommended.

Congenital Titinopathy: Comprehensive characterization and pathogenic insights.

OBJECTIVE: Comprehensive clinical characterization of congenital titinopathy to facilitate diagnosis and management of this important emerging disorder. METHODS: Using massively parallel sequencing we identified 30 patients from 27 families with 2 pathogenic nonsense, frameshift and/or splice site TTN mutations in trans. We then undertook a detailed analysis of the clinical, histopathological and imaging features of these patients. RESULTS: All patients had prenatal or early onset hypotonia and/or congenital contractures. None had ophthalmoplegia. Scoliosis and respiratory insufficiency typically developed early and progressed rapidly, whereas limb weakness was often slowly progressive, and usually did not prevent independent walking. Cardiac involvement was present in 46% of patients. Relatives of 2 patients had dilated cardiomyopathy. Creatine kinase levels were normal to moderately elevated. Increased fiber size variation, internalized nuclei and cores were common histopathological abnormalities. Cap-like regions, whorled or ring fibers, and mitochondrial accumulations were also observed. Muscle magnetic resonance imaging showed gluteal, hamstring and calf muscle involvement. Western blot analysis showed a near-normal sized titin protein in all samples. The presence of 2 mutations predicted to impact both N2BA and N2B cardiac isoforms appeared to be associated with greatest risk of cardiac involvement. One-third of patients had 1 mutation predicted to impact exons present in fetal skeletal muscle, but not included within the mature skeletal muscle isoform transcript. This strongly suggests developmental isoforms are involved in the pathogenesis of this congenital/early onset disorder. INTERPRETATION: This detailed clinical reference dataset will greatly facilitate diagnostic confirmation and management of patients, and has provided important insights into disease pathogenesis. Ann Neurol 2018;83:1105-1124.

Sarcolemmal excitability in the myotonic dystrophies.

INTRODUCTION: Chloride conductance disturbances contribute to sarcolemmal dysfunction in myotonic dystrophy type 1 (DM1) and type 2 (DM2). Studies using muscle velocity recovery cycles (MVRCs) suggest Na+ /K+ -adenosine triphosphatase activation becomes defective in advanced DM1. We used MVRCs to investigate muscle excitability in DM1 and DM2. METHODS: MVRCs were measured for patients with mild (n = 8) and advanced (n = 11) DM1, DM2 (n = 4), and normal controls (n = 30). RESULTS: Residual supernormality after multiple conditioning stimuli was increased in DM2 and advanced DM1. Advanced DM1 was distinguished by increases in muscle relative refractory period (MRRP) and reduced early supernormality as well as peak amplitude decrements for the first and last responses in train during repetitive stimulation. DISCUSSION: Prolongation of the MRRP indicates that depolarization of the resting muscle membrane potential occurs in advanced DM1, with possible implications for future therapeutic approaches. Muscle Nerve 57: 595-602, 2018.

Effect of Obstructive Sleep Apnea Treatment on Renal Function in Patients with Cardiovascular Disease.

RATIONALE: Obstructive sleep apnea (OSA) is associated with impaired renal function, but uncertainty exists over whether OSA treatment can influence renal outcomes. OBJECTIVES: To determine the effects of continuous positive airway pressure (CPAP) on renal function in subjects with coexisting OSA and cardiovascular disease. METHODS: This was a substudy of the international SAVE (Sleep Apnea Cardiovascular Endpoints) trial, in which 2,717 patients with moderate to severe OSA and established coronary or cerebrovascular disease were randomized to receive either CPAP plus usual care or usual care alone. Renal function and adverse renal events were compared between the CPAP (n = 102) and usual care (n = 98) groups. Glomerular filtration rate was estimated at randomization and at the end of follow-up, and the urinary albumin-to-creatinine ratio was measured at study exit. MEASUREMENTS AND MAIN RESULTS: In 200 substudy participants (mean age, 64 yr; median, 4% oxygen desaturation index; 20 events/h; mean estimated glomerular filtration rate at baseline, 82 ml/min/1.73 m2), the median (interquartile range) changes in estimated glomerular filtration rate (ml/min/1.73 m2/yr) were -1.64 (-3.45 to -0.740) in the CPAP group and -2.30 (-4.53 to -0.71) in the usual care group (P = 0.21) after a median of 4.4 years. There were no between-group differences in end-of-study urinary albumin-to-creatinine ratio or in the occurrence of serious renal or urinary adverse events during the trial. The level of CPAP adherence did not influence the findings. CONCLUSIONS: CPAP treatment of OSA in patients with cardiovascular disease does not alter renal function or the occurrence of renal adverse events. Clinical trial registered with www.clinicaltrials.gov (NCT00738179).

Bone health in facioscapulohumeral muscular dystrophy: A cross-sectional study.

INTRODUCTION: Herein we provide a comprehensive overview of bone health in facioscapulohumeral muscular dystrophy (FSHD). METHODS: Ninety-four adult individuals with FSHD type 1 from 2 sites were included in this cross-sectional study. Clinical characteristics and determinants of bone health were examined. Relationships between bone mineral density (BMD), strength, and function were explored. RESULTS: Nearly a third of subjects were deficient in vitamin D3 . Mean whole-body BMD z-score was -0.7; 11% of subjects had greater than age-related reductions in whole-body BMD (z-score < -2.0). Whole-body and regional BMDs were associated with strength and function. Thirty-six percent had a history of fractures. Likelihood of fractures was reduced for those with normal whole-body BMD (odds ratio = 0.25, 95% confidence interval 0.04-0.78). DISCUSSION: A diagnosis of FSHD is not necessarily predictive of reduced BMD or increased fracture rate. Given the considerable variability of bone health in the FSHD population, strength and function can serve as predictors of BMD. Muscle Nerve 56: 1108-1113, 2017.

Mortality and Causes of Death in Patients with Sporadic Inclusion Body Myositis: Survey Study Based on the Clinical Experience of Specialists in Australia, Europe and the USA.

BACKGROUND: There is a paucity of data on mortality and causes of death (CoDs) in patients with sporadic inclusion body myositis (sIBM), a rare, progressive, degenerative, inflammatory myopathy that typically affects those aged over 50 years. OBJECTIVE: Based on patient records and expertise of clinical specialists, this study used questionnaires to evaluate physicians' views on clinical characteristics of sIBM that may impact on premature mortality and CoDs in these patients. METHODS: Thirteen physicians from seven countries completed two questionnaires online between December 20, 2012 and January 15, 2013. Responses to the first questionnaire were collated and presented in the second questionnaire to seek elaboration and identify consensus. RESULTS: All 13 physicians completed both questionnaires, providing responses based on 585 living and 149 deceased patients under their care. Patients were reported to have experienced dysphagia (60.2%) and injurious falls (44.3%) during their disease. Over half of physicians reported that a subset of their patients with sIBM had a shortened lifespan (8/13), and agreed that bulbar dysfunction/dysphagia/oropharyngeal involvement (12/13), early-onset disease (8/13), severe symptoms (8/13), and falls (7/13) impacted lifespan. Factors related to sIBM were reported as CoDs in 40% of deceased patients. Oropharyngeal muscle dysfunction was ranked as the leading feature of sIBM that could contribute to death. The risk of premature mortality was higher than the age-matched comparison population. CONCLUSIONS: In the absence of data from traditional sources, this study suggests that features of sIBM may contribute to premature mortality and may be used to inform future studies.

Use of Whole-Exome Sequencing for Diagnosis of Limb-Girdle Muscular Dystrophy: Outcomes and Lessons Learned.

IMPORTANCE: To our knowledge, the efficacy of transferring next-generation sequencing from a research setting to neuromuscular clinics has never been evaluated. OBJECTIVE: To translate whole-exome sequencing (WES) to clinical practice for the genetic diagnosis of a large cohort of patients with limb-girdle muscular dystrophy (LGMD) for whom protein-based analyses and targeted Sanger sequencing failed to identify the genetic cause of their disorder. DESIGN, SETTING, AND PARTICIPANTS: We performed WES on 60 families with LGMDs (100 exomes). Data analysis was performed between January 6 and December 19, 2014, using the xBrowse bioinformatics interface (Broad Institute). Patients with LGMD were ascertained retrospectively through the Institute for Neuroscience and Muscle Research Biospecimen Bank between 2006 and 2014. Enrolled patients had been extensively investigated via protein studies and candidate gene sequencing and remained undiagnosed. Patients presented with more than 2 years of muscle weakness and with dystrophic or myopathic changes present in muscle biopsy specimens. MAIN OUTCOMES AND MEASURES: The diagnostic rate of LGMD in Australia and the relative frequencies of the different LGMD subtypes. Our central goals were to improve the genetic diagnosis of LGMD, investigate whether the WES platform provides adequate coverage of known LGMD-related genes, and identify new LGMD-related genes. RESULTS: With WES, we identified likely pathogenic mutations in known myopathy genes for 27 of 60 families. Twelve families had mutations in known LGMD-related genes. However, 15 families had variants in disease-related genes not typically associated with LGMD, highlighting the clinical overlap between LGMD and other myopathies. Common causes of phenotypic overlap were due to mutations in congenital muscular dystrophy-related genes (4 families) and collagen myopathy-related genes (4 families). Less common myopathies included metabolic myopathy (2 families), congenital myasthenic syndrome (DOK7), congenital myopathy (ACTA1), tubular aggregate myopathy (STIM1), myofibrillar myopathy (FLNC), and mutation of CHD7, usually associated with the CHARGE syndrome. Inclusion of family members increased the diagnostic efficacy of WES, with a diagnostic rate of 60% for "trios" (an affected proband with both parents) vs 40% for single probands. A follow-up screening of patients whose conditions were undiagnosed on a targeted neuromuscular disease-related gene panel did not improve our diagnostic yield. CONCLUSIONS AND RELEVANCE: With WES, we achieved a diagnostic success rate of 45.0% in our difficult-to-diagnose cohort of patients with LGMD. We expand the clinical phenotypes associated with known myopathy genes, and we stress the importance of accurate clinical examination and histopathological results for interpretation of WES, with many diagnoses requiring follow-up review and ancillary investigations of biopsy specimens or serum samples.

Expanding the phenotype of GMPPB mutations.

Dystroglycanopathies are a heterogeneous group of diseases with a broad phenotypic spectrum ranging from severe disorders with congenital muscle weakness, eye and brain structural abnormalities and intellectual delay to adult-onset limb-girdle muscular dystrophies without mental retardation. Most frequently the disease onset is congenital or during childhood. The exception is FKRP mutations, in which adult onset is a common presentation. Here we report eight patients from five non-consanguineous families where next generation sequencing identified mutations in the GMPPB gene. Six patients presented as an adult or adolescent-onset limb-girdle muscular dystrophy, one presented with isolated episodes of rhabdomyolysis, and one as a congenital muscular dystrophy. This report expands the phenotypic spectrum of GMPPB mutations to include limb-girdle muscular dystrophies with adult onset with or without intellectual disability, or isolated rhabdomyolysis.

Analysis of HLA-DRB3 alleles and supertypical genotypes in the MHC Class II region in sporadic inclusion body myositis.

We compared the carriage frequencies of HLA-DRB3 and its major alleles and of HLA-DRB4 and HLA-DRB5 in an Australian sIBM cohort and a population control group who had previously been genotyped for the HLA-DRB1*03:01 risk allele. There was a strong disease association with the carriage of the DRB3*01:01 allele which was accounted for by its linkage disequilibrium with DRB1*03:01. The carriage of HLA-DRB4 was found to be strongly protective and abrogated the risk effect of HLA-DRB1*03:01. The findings indicate that haplotypic combinations of alleles at the HLA-DRB1 and secondary HLA-DRB loci have important risk modifying effects in sIBM.

High-resolution HLA-DRB1 genotyping in an Australian inclusion body myositis (s-IBM) cohort: an analysis of disease-associated alleles and diplotypes.

We performed high-resolution (4-digit) HLA-DRB1 genotyping in an Australian cohort of 105s-IBM patients and 189 controls. Our findings showed that whilst the strongest association was with the HLA-DRB1*03:01 allele and the HLA-DRB1*03:01/*01:01 diplotype, HLA-DRB1*01:01 and HLA-DRB1*13:01 are also risk alleles. A number of other alleles, HLA-DRB1*04:01, *04:04, *07:01, *09:01, *11:01 and *15:01, as well as the HLA-DRB1*03:01/*04:01 and HLA-DRB1*03:01/*07:01 diplotypes were reduced in s-IBM cases and may be protective. The HLA-DRB1*03:01 and HLA-DRB1*13:01 alleles also appear to have an influence on the age at onset of the disease and severity of muscle weakness. Our findings indicate that the influence of HLA-DRB1 in s-IBM is complex and that epistatic interactions at the HLA-DRB1 locus contribute both to disease susceptibility and to the clinical phenotype.

Abnormal ventilatory control in Parkinson's disease--further evidence for non-motor dysfunction.

There has been increasing recognition of pre-motor manifestations of Parkinson's disease (PD) resulting from early brainstem involvement. We sought to determine whether ventilatory control is abnormal. Patients with PD without respiratory disease were recruited. Spirometry, lung volumes, diffusing capacity and respiratory muscle strength were assessed. Occlusion pressure and ventilation were measured with increasing CO(2). Arterial blood gases were taken at rest and following 20 min exposure to 15% O(2). A linear correlation assessed associations between respiratory function and indices of PD severity. 19 subjects (17 males) with mild-moderate PD were studied (mean (SD) age 66 (8) years). Respiratory flows and volumes were normal in 16/19. Maximum inspiratory and expiratory pressures were below LLN in 13/19 and 15/19 respectively. 7/15 had a reduced ventilatory response to hypercapnia and 11/15 had an abnormal occlusion pressure. There was no correlation between impairment of ventilatory response and reduction in respiratory muscle strength. Response to mild hypoxia was normal and there were no associations between disease severity and respiratory function. Our findings suggest that patients with mild-moderate PD have abnormal ventilatory control despite normal lung volumes and flows.

Sporadic inclusion body myositis: HLA-DRB1 allele interactions influence disease risk and clinical phenotype.

Susceptibility to sIBM is strongly associated with the HLA-DRB1*03 allele and the 8.1 MHC ancestral haplotype (HLA-A1, B8, DRB1*03) but little is known about the effects of allelic interactions at the DRB1 locus or disease-modifying effects of HLA alleles. HLA-A, B and DRB1 genotyping was performed in 80 Australian sIBM cases and the frequencies of different alleles and allele combinations were compared with those in a group of 190 healthy controls. Genotype-phenotype correlations were also investigated. Amongst carriers of the HLA-DRB1*03 allele, DRB1*03/*01 heterozygotes were over-represented in the sIBM group (p<0.003) while. DRB1*03/*04 heterozygotes were under-represented (p<0.008). The mean age-at-onset (AAO) was 6.5 years earlier in DRB1*03/*01 heterozygotes who also had more severe quadriceps muscle weakness than the rest of the cohort. The findings indicate that interactions between the HLA-DRB1*03 allele and other alleles at the DRB1 locus can influence disease susceptibility and the clinical phenotype in sIBM.