<Emphasis Type="Italic">HTT</Emphasis> Gene Premutation Allele Frequencies in the Russian Federation

Huntington disease (Huntington chorea, HD) is a severe neurodegenerative disease determined by polyglutamine. Polyglutamine expansion in exon 1 of the HTT gene causes Huntington disease. To date, less than 35 CAG triplets are suggested to be present in normal alleles. Alleles bearing from 27 to 35 CAG repeats are generally considered as intermediate or premutation. Alleles with the number of CAG repeats varying from 36 to 39 demonstrate reduced penetrance and result in late manifestation of the disease. To date, no studies based on representative samples of Russian residents estimating the frequencies of premutation and alleles with reduced penetrance have been published. Meanwhile, this is extremely important for genetic counseling of patients bearing such alleles and for the calculation of risks for their offspring. In the present study, the analysis of samples of Russian patients with incoming diagnoses of Huntington chorea (N = 1092), Wilson–Konovalov disease (N = 333), Hallervorden–Spatz disease (N = 33) and a control group consisting of 230 unexamined individuals from the Russian Federation under 45 years of age was carried out. A spectrum of CAG repeat length in the HTT gene in patients with HD was obtained. Patients with HD were detected in the samples of patients with incoming diagnoses of Wilson–Konovalov disease and Hallervorden–Spatz disease. This observation indicates the complexity of differential diagnosis of these diseases. An assumption was made that an allele with 36 CAG repeats should be classified as premutation. We confirmed the previously observed trend for the increased number of CAG repeats in the case of paternal transmission of the mutant allele. The frequency of premutation allele of 2.6% in Russian residents was established.     

A Unified Rapid PCR Method for Detection of Normal and Expanded Trinucleotide Alleles of CAG Repeats in Huntington Chorea and CGG Repeats in Fragile X Syndrome

We report on a unified rapid betaine-based-PCR protocol for amplification of the (CAG)n region in Huntington disease (HD) and the (CGG)n region in Fragile X syndrome (FXS), followed by an electrophoretic separation on automated sequencer for precise determination of the triplet numbers. The high betaine concentration (2.5 M betaine) permits precise amplification of the CAG and CGG repeats. Ten HD affected patients and 10 healthy individuals from HD families were re-evaluated. For FXS the CGG region in normal individuals and premutations of about 100 repeats were precisely amplified by this protocol. Ten unrelated FXS premutation carriers and 24 mentally retarded non-FXS affected boys were re-examined by this method. The results totally coincided with the previous ones. This protocol is a good choice as a fast screening test. Within 24 h we can have preliminary information on the patient’s genetic status. Normal individuals, CGG premutation carriers up to 100 repeats, as well as HD patients carrying an expansion up to 50 CAG repeats can be easily clarified. This accounts for a relatively large proportion (about 90%) of the suspected HD and FXS patients, referred to our laboratory for genetic analysis. The calculation of the repeat’s number is more accurate for the correct interpretation of the results, screening tests and genetic counselling.     

Phenotypic Characterization of Individuals with 30–40 CAG Repeats in the Huntington Disease (HD) Gene Reveals HD Cases with 36 Repeats and Apparently Normal Elderly Individuals with 36–39 Repeats

Abnormal CAG expansions in the IT-15 gene are associated with Huntington disease (HD). In the diagnostic setting it is necessary to define the limits of the CAG size ranges on normal and HD-associated chromosomes. Most large analyses that defined the limits of the normal and pathological size ranges employed PCR assays, which included the CAG repeats and a CCG repeat tract that was thought to be invariant. Many of these experiments found an overlap between the normal and disease size ranges. Subsequent findings that the CCG repeats vary by 8 trinucleotide lengths suggested that the limits of the normal and disease size ranges should be reevaluated with assays that exclude the CCG polymorphism. Since patients with between 30 and 40 repeats are rare, a consortium was assembled to collect such individuals.All 178 samples were reanalyzed in Cambridge by using assays specific for the CAG repeats. We have optimized methods for reliable sizing of CAG repeats and show cases that demonstrate the dangers of using PCR assays that include both the CAG and CCG polymorphisms. Seven HD patients had 36 repeats, which confirms that this allele is associated with disease. Individuals without apparent symptoms or signs of HD were found at 36 repeats (aged 74, 78, 79, and 87 years), 37 repeats (aged 69 years), 38 repeats (aged 69 and 90 years), and 39 repeats (aged 67, 90, and 95 years). The detailed case histories of an exceptional case from this series will be presented: a 95-year-old man with 39 repeats who did not have classical features of HD. The apparently healthy survival into old age of some individuals with 36–39 repeats suggests that the HD mutation may not always be fully penetrant.     

Quantification of age-dependent somatic CAG repeat instability in Hdh CAG knock-in mice reveals different expansion dynamics in striatum and liver

Background

Age at onset of Huntington''s disease (HD) is largely determined by the CAG trinucleotide repeat length in the HTT gene. Importantly, the CAG repeat undergoes tissue-specific somatic instability, prevalent in brain regions that are disease targets, suggesting a potential role for somatic CAG repeat instability in modifying HD pathogenesis. Thus, understanding underlying mechanisms of somatic CAG repeat instability may lead to discoveries of novel therapeutics for HD. Investigation of the dynamics of the CAG repeat size changes over time may provide insights into the mechanisms underlying CAG repeat instability.

Methodology/Principal Findings

To understand how the HTT CAG repeat length changes over time, we quantified somatic instability of the CAG repeat in Huntington''s disease CAG knock-in mice from 2–16 months of age in liver, striatum, spleen and tail. The HTT CAG repeat in spleen and tail was very stable, but that in liver and striatum expanded over time at an average rate of one CAG per month. Interestingly, the patterns of repeat instability were different between liver and striatum. Unstable CAG repeats in liver repeatedly gained similar sizes of additional CAG repeats (approximately two CAGs per month), maintaining a distinct population of unstable repeats. In contrast, unstable CAG repeats in striatum gained additional repeats with different sizes resulting in broadly distributed unstable CAG repeats. Expanded CAG repeats in the liver were highly enriched in polyploid hepatocytes, suggesting that the pattern of liver instability may reflect the restriction of the unstable repeats to a unique cell type.

Conclusions/Significance

Our results are consistent with repeat expansion occurring as a consequence of recurrent small repeat insertions that differ in different tissues. Investigation of the specific mechanisms that underlie liver and striatal instability will contribute to our understanding of the relationship between instability and disease and the means to intervene in this process.     

Phonatory Dysfunction as a Preclinical Symptom of Huntington Disease

Purpose

Although dysphonia has been shown to be a common sign of Huntington disease (HD), the extent of phonatory dysfunction in gene positive premanifest HD individuals remains unknown. The aim of the current study was to explore the possible occurrence of phonatory abnormalities in prodromal HD.

Method

Sustained vowel phonations were acquired from 28 premanifest HD individuals and 28 healthy controls of comparable age. Data were analysed acoustically for measures of several phonatory dimensions including airflow insufficiency, aperiodicity, irregular vibration of vocal folds, signal perturbations, increased noise, vocal tremor and articulation deficiency. A predictive model was built to find the best combination of acoustic features and estimate sensitivity/specificity for differentiation between premanifest HD subjects and controls. The extent of voice deficits according to a specific phonatory dimension was determined using statistical decision making theory. The results were correlated to global motor function, cognitive score, disease burden score and estimated years to disease onset.

Results

Measures of aperiodicity and increased noise were able to significantly differentiate between premanifest HD individuals and controls (p<0.01). The combination of these aspects of dysphonia led to a sensitivity of 91.5% and specificity of 79.2% to correctly distinguish speakers with premanifest HD from healthy individuals. Some form of disrupted phonatory function was revealed in 68% of our premanifest HD subjects, where 18% had one affected phonatory dimension and 50% showed impairment of two or more dimensions. A relationship between pitch control and cognitive score was also observed (r = −0.50, p = 0.007).

Conclusions

Phonatory abnormalities are detectable even the in premotor stages of HD. Speech investigation may have the potential to provide functional biomarkers of HD and could be included in future clinical trials and therapeutic interventions.     

Counting CAG repeats in the Huntington’s disease gene by restriction endonuclease EcoP15I cleavage

Huntington’s disease (HD) is a progressive neurodegenerative disorder with autosomal-dominant inheritance. The disease is caused by a CAG trinucleotide repeat expansion located in the first exon of the HD gene. The CAG repeat is highly polymorphic and varies from 6 to 37 repeats on chromosomes of unaffected individuals and from more than 30 to 180 repeats on chromosomes of HD patients. In this study, we show that the number of CAG repeats in the HD gene can be determined by restriction of the DNA with the endonuclease EcoP15I and subsequent analysis of the restriction fragment pattern by electrophoresis through non-denaturing polyacrylamide gels using the ALFexpress DNA Analysis System. CAG repeat numbers in the normal (30 and 35 repeats) as well as in the pathological range (81 repeats) could be accurately counted using this assay. Our results suggest that this high-resolution method can be used for the exact length determination of CAG repeats in HD genes as well as in genes affected in related CAG repeat disorders.     

Sequence-Level Analysis of the Major European Huntington Disease Haplotype

Huntington disease (HD) reflects the dominant consequences of a CAG-repeat expansion in HTT. Analysis of common SNP-based haplotypes has revealed that most European HD subjects have distinguishable HTT haplotypes on their normal and disease chromosomes and that ∼50% of the latter share the same major HD haplotype. We reasoned that sequence-level investigation of this founder haplotype could provide significant insights into the history of HD and valuable information for gene-targeting approaches. Consequently, we performed whole-genome sequencing of HD and control subjects from four independent families in whom the major European HD haplotype segregates with the disease. Analysis of the full-sequence-based HTT haplotype indicated that these four families share a common ancestor sufficiently distant to have permitted the accumulation of family-specific variants. Confirmation of new CAG-expansion mutations on this haplotype suggests that unlike most founders of human disease, the common ancestor of HD-affected families with the major haplotype most likely did not have HD. Further, availability of the full sequence data validated the use of SNP imputation to predict the optimal variants for capturing heterozygosity in personalized allele-specific gene-silencing approaches. As few as ten SNPs are capable of revealing heterozygosity in more than 97% of European HD subjects. Extension of allele-specific silencing strategies to the few remaining homozygous individuals is likely to be achievable through additional known SNPs and discovery of private variants by complete sequencing of HTT. These data suggest that the current development of gene-based targeting for HD could be extended to personalized allele-specific approaches in essentially all HD individuals of European ancestry.     

The likelihood of being affected with Huntington disease by a particular age, for a specific CAG size.

Prior studies describing the relationship between CAG size and the age at onset of Huntington disease (HD) have focused on affected persons. To further define the relationship between CAG repeat size and age at onset of HD, we now have analyzed a large cohort of affected and asymptomatic at-risk persons with CAG expansion. This cohort numbered 1,049 persons, including 321 at-risk and 728 affected individuals with a CAG size of 29-121 repeats. Kaplan-Meier analysis has provided curves for determining the likelihood of onset at a given age, for each CAG repeat length in the 39-50 range. The curves were significantly different (P < .0005), with relatively narrow 95% confidence intervals (95% CI) (+/-10%). Penetrance of the mutation for HD also was examined. Although complete penetrance of HD was observed for CAG sizes of > or = 42, only a proportion of those with a CAG repeat length of 36-41 showed signs or symptoms of HD within a normal life span. These data provide information concerning the likelihood of being affected, by a specific age, with a particular CAG size, and they may be useful in predictive-testing programs and for the design of clinical trials for persons at increased risk for HD.     

Androgen receptor CAG polymorphism and prostate cancer risk

Recent studies have suggested that polymorphisms of the androgen receptor gene ( AR) may influence the risk of prostate cancer (PC) development and progression. Here, we analyzed the length of the CAG repeat of the AR gene in 1363 individuals, including patients with PC, benign prostate hyperplasia (BPH), and population controls. There was a tendency for short CAG repeats to be associated with PC. The Odds Ratio (OR) for PC was 1.47 ( P=0.05) when individuals with short CAG repeats (18). CAG repeat length was not significantly associated with family history, disease stage, grade, age at diagnosis, prostate-specific antigen (PSA) level at diagnosis, or prognosis of the patients. Unexpectedly, short CAG repeats were significantly less common in patients with BPH compared with controls (OR=0.47, P=0.03). Our results suggest that the CAG polymorphism of the AR gene is unlikely to have a major role in the development or progression of PC in the Finnish population. The association of CAG repeats with the risk of BPH warrants further study.     

Huntington's disease: a clinical review

Huntington disease (HD) is a rare neurodegenerative disorder of the central nervous system characterized by unwanted choreatic movements, behavioral and psychiatric disturbances and dementia. Prevalence in the Caucasian population is estimated at 1/10,000-1/20,000. Mean age at onset of symptoms is 30-50 years. In some cases symptoms start before the age of 20 years with behavior disturbances and learning difficulties at school (Juvenile Huntington's disease; JHD). The classic sign is chorea that gradually spreads to all muscles. All psychomotor processes become severely retarded. Patients experience psychiatric symptoms and cognitive decline. HD is an autosomal dominant inherited disease caused by an elongated CAG repeat (36 repeats or more) on the short arm of chromosome 4p16.3 in the Huntingtine gene. The longer the CAG repeat, the earlier the onset of disease. In cases of JHD the repeat often exceeds 55. Diagnosis is based on clinical symptoms and signs in an individual with a parent with proven HD, and is confirmed by DNA determination. Pre-manifest diagnosis should only be performed by multidisciplinary teams in healthy at-risk adult individuals who want to know whether they carry the mutation or not. Differential diagnoses include other causes of chorea including general internal disorders or iatrogenic disorders. Phenocopies (clinically diagnosed cases of HD without the genetic mutation) are observed. Prenatal diagnosis is possible by chorionic villus sampling or amniocentesis. Preimplantation diagnosis with in vitro fertilization is offered in several countries. There is no cure. Management should be multidisciplinary and is based on treating symptoms with a view to improving quality of life. Chorea is treated with dopamine receptor blocking or depleting agents. Medication and non-medical care for depression and aggressive behavior may be required. The progression of the disease leads to a complete dependency in daily life, which results in patients requiring full-time care, and finally death. The most common cause of death is pneumonia, followed by suicide.     

Lymphoma discrimination by computerized triple matrix analysis of list mode data from three-color flow cytometric immunophenotypes of bone marrow aspirates

BACKGROUND: The goal of this study was to evaluate a self-learning algorithm for the computer classification of information extracted from flow cytometric immunophenotype list mode files from high-grade non-Hodgkin's lymphoma (NHL), Hodgkin's disease (HD), and multiple myeloma (MM). Materials and Methods Bone marrow aspirates (BMA) were obtained from untreated NHL (n = 51), HD (n = 9), or MM (n = 13) patients. Bone marrow aspirates were not infiltrated in NHL and HD patients as confirmed by thorough histologic and cytologic investigation; however, MM patients showed an infiltration rate >50% by malignant myeloma cells. Peripheral blood leukocyte (PBL) samples were taken from age-matched healthy volunteers (n = 44) as easily available control material. A second control group of 15 healthy volunteers, from whom BMA and PBL samples were available, allowed us to differentiate whether the observed classification results on malignant samples were due to the malignant process or simply to the inherent differences between BMA and PBL. Bone marrow aspirates and PBL were analyzed by the same immunophenotyping antibody panel (CD45/14/20, CD4/8/3, kappa/CD19/5, lambda/CD19/5). The acquired list mode data files were analyzed and classified by the self-learning triple matrix classification algorithms CLASSIF1 following a priori separation of the data into a learning set and unknown test set. After completion of the learning phase, known patient samples were reclassified and unknown samples prospectively classified by the algorithm. RESULTS: Highly discriminatory information was extracted for the various lymphoma entities. The most discriminating information was encountered in antibody binding, antibody binding ratios, and relative antibody surface density parameters of leukocytes rather than in percentage frequencies of discrete leukocyte subpopulations. Samples from healthy controls were classified as normal in 97.2% of the cases, whereas those of NHL, HD, and MM patients were on average correctly classified in 80. 8% of the cases. CONCLUSIONS: Although no detectable lymphoma cells were present in BMA of NHL and HD patients, the CLASSIF1 classification of the immunophenotypes of morphologically normal cells provided a surprisingly good disease discrimination equal or better than that obtained by examining pathological lymph nodes according to the respective literature. The results are suggestive for a lymphoma-related and disease-specific antigen expression shift on normal hematopoietic bone marrow cells that can be used to discriminate the underlying disease (specificity of unspecific changes), i.e., in this case NHL from HD. Multiple myeloma patients were discriminated by changes on malignant as well as on normal bone marrow cells.     

Prevalence and Impact on Stroke in Patients Receiving Maintenance Hemodialysis versus Peritoneal Dialysis: A Prospective Observational Study

Background

Patients undergoing maintenance dialysis are at increased risk of stroke, however, less is known about the prevalence and impact on stroke in the patients.

Methods

In this prospective cohort study, 590 patients undergoing hemodialysis (HD; n = 285) or peritoneal dialysis (PD; n = 305) from January 1, 2008 to December 31, 2012 were recruited. Baseline demographic, clinical, and laboratory data were collected. Timeline incidence data were analyzed using a Poisson model. The Cox proportional hazards regression assessed adjusted differences in stroke risk, a multivariate analysis was also performed.

Results

62 strokes occurred during 1258 total patient-years of follow-up. Stroke occurred at a rate of 49.2/1,000 patient-years with a predominance in HD patients compared with PD patients (74.0 vs. 31.8/1,000 patient-years). The cumulative hazard of developing stroke was significantly higher in HD patients (hazard ratio [HR], 1.75; 95% confidence interval [CI], 1.15–3.62; p = 0.046) after adjusting for potential confounders. HD patients had an increased risk of ischemic stroke (HR, 2.62; 95% CI, 1.56–4.58; p = 0.002). The risk of hemorrhagic stroke was not significantly different between PD and HD patients. On multivariate Cox analysis, risk factors of stroke in both HD and PD patients were older age, diabetes, and cardiovascular disease. Other independent risk factors of stroke were lower albumin-corrected calcium in HD patients and higher triglycerides in PD patients.

Conclusions

Patients undergoing PD were less likely to develop ischemic stroke than those undergoing HD. Comprehensive control of diabetes, cardiovascular disease, calcium-phosphorus metabolism, and triglyceride levels may be useful preventive strategies for stroke in dialysis patients.     

Trinucleotide (CAG) repeat expansion in chromosomes of Spanish patients with Huntington's disease

Huntington's disease (HD) is a neurodegenerative and hereditary disease characterized by progressive movement disorders and mental and behavioral abnormalities. The HD gene is an expanding and unstable trinucleotide repeat (CAG repeat sequences). We studied 77 individuals from 38 families with HD in an attempt to obtain information for genetic counselling and differential diagnosis. Our results indicate that individuals with more than 40 repeats will be affected by the disease, whereas those with fewer than 30 will be healthy. There can be some overlap between 30 and 40 repeats, and one should be careful when interpreting these results.     

High-Flux Hemodialysis and High-Volume Hemodiafiltration Improve Serum Calcification Propensity

BackgroundCalciprotein particles (CPPs) may play an important role in the calcification process. The calcification propensity of serum (T₅₀) is highly predictive of all-cause mortality in chronic kidney disease patients. Whether T₅₀ is therapeutically improvable, by high-flux hemodialysis (HD) or hemodiafiltration (HDF), has not been studied yet.MethodsWe designed a cross-sectional single center study, and included stable prevalent in-center dialysis patients on HD or HDF. Patients were divided into two groups based on dialysis modality, were on a thrice-weekly schedule, had a dialysis vintage of > 3 months and vascular access providing a blood flow rate > 300 ml/min. Calcification propensity of serum was measured by the time of transformation from primary to secondary CPP (T₅₀ test), by time-resolved nephelometry.ResultsWe included 64 patients, mean convective volume was 21.7L (SD 3.3L). In the pooled analysis, T₅₀ levels increased in both the HD and HDF group with pre- and post-dialysis (mean (SD)) of 244(64) - 301(57) and 253(55) - 304(61) min respectively (P = 0.43(HD vs. HDF)). The mean increase in T₅₀ was 26.29% for HD and 21.97% for HDF patients (P = 0.61 (HD vs. HDF)). The delta values (Δ) of calcium, phosphate and serum albumin were equal in both groups. Baseline T₅₀ was negatively correlated with phosphate, and positively correlated with serum magnesium and fetuin-A. The ΔT₅₀ was mostly influenced by Δ phosphate (r = -0.342; P = 0.002 HD and r = -0.396; P<0.001 HDF) in both groups.ConclusionsHD and HDF patients present with same baseline T50 calcification propensity values pre-dialysis. Calcification propensity is significantly improved during both HD and HDF sessions without significant differences between both modalities.     

Counting CAG repeats in the Huntington's disease gene by restriction endonuclease EcoP15I cleavage

Huntington's disease (HD) is a progressive neurodegenerative disorder with autosomal-dominant inheritance. The disease is caused by a CAG trinucleotide repeat expansion located in the first exon of the HD gene. The CAG repeat is highly polymorphic and varies from 6 to 37 repeats on chromosomes of unaffected individuals and from more than 30 to 180 repeats on chromosomes of HD patients. In this study, we show that the number of CAG repeats in the HD gene can be determined by restriction of the DNA with the endonuclease EcoP15I and subsequent analysis of the restriction fragment pattern by electrophoresis through non-denaturing polyacrylamide gels using the ALFexpress DNA Analysis System. CAG repeat numbers in the normal (30 and 35 repeats) as well as in the pathological range (81 repeats) could be accurately counted using this assay. Our results suggest that this high-resolution method can be used for the exact length determination of CAG repeats in HD genes as well as in genes affected in related CAG repeat disorders.     

Multiple diagnostic techniques identify previously vaccinated individuals with protective immunity against monkeypox

Approximately 50% of the US population received smallpox vaccinations before routine immunization ceased in 1972 for civilians and in 1990 for military personnel. Several studies have shown long-term immunity after smallpox vaccination, but skepticism remains as to whether this will translate into full protection against the onset of orthopoxvirus-induced disease. The US monkeypox outbreak of 2003 provided the opportunity to examine this issue. Using independent and internally validated diagnostic approaches with >or=95% sensitivity and >or=90% specificity for detecting clinical monkeypox infection, we identified three previously unreported cases of monkeypox in preimmune individuals at 13, 29 and 48 years after smallpox vaccination. These individuals were unaware that they had been infected because they were spared any recognizable disease symptoms. Together, this shows that the US monkeypox outbreak was larger than previously realized and, more importantly, shows that cross-protective antiviral immunity against West African monkeypox can potentially be maintained for decades after smallpox vaccination.     

两个亨廷顿舞蹈病家系IT15基因的研究

为了探讨亨廷顿舞蹈病家系患者的临床特征与IT15基因中(CAG)_n重复拷贝数之间的相互关系, 对两家系患者的临床、影像学特征、发病年龄及遗传方式等进行分析; 用聚合酶链反应技术、6%聚丙烯酰胺凝胶电泳及直接测序等方法, 对42名家系成员的IT15基因的(CAG)_n三核苷酸重复序列进行分析。结果显示家系1患者无典型的临床“三联症”及尾状核的萎缩, 18名家系成员中9名患者IT15基因的(CAG)_n拷贝数介于40~50次之间,拷贝数与发病年龄无明显相关; 而家系2患者具有典型的“三联症”和尾状核的萎缩, 24名家系成员中5例患者(CAG)_n拷贝数大于等于50次, 发病年龄与(CAG)_n拷贝数相关。因此亨廷顿舞蹈病患者的临床特征在一定程度上受IT15基因的(CAG)_n三核苷酸重复拷贝数的影响, 拷贝数大于50次, 发病年龄与(CAG)_n拷贝数相关, 并有经父系遗传的(CAG)_n拷贝数的扩展, 且存在遗传早现现象。     

Temporal estimates of case-fatality rate for COVID-19 outbreaks in Canada and the United States

BACKGROUND:Estimates of the case-fatality rate (CFR) associated with coronavirus disease 2019 (COVID-19) vary widely in different population settings. We sought to estimate and compare the COVID-19 CFR in Canada and the United States while adjusting for 2 potential biases in crude CFR.METHODS:We used the daily incidence of confirmed COVID-19 cases and deaths in Canada and the US from Jan. 31 to Apr. 22, 2020. We applied a statistical method to minimize bias in the crude CFR by accounting for the survival interval as the lag time between disease onset and death, while considering reporting rates of COVID-19 cases less than 50% (95% confidence interval 10%–50%).RESULTS:Using data for confirmed cases in Canada, we estimated the crude CFR to be 4.9% on Apr. 22, 2020, and the adjusted CFR to be 5.5% (credible interval [CrI] 4.9%–6.4%). After we accounted for various reporting rates less than 50%, the adjusted CFR was estimated at 1.6% (CrI 0.7%–3.1%). The US crude CFR was estimated to be 5.4% on Apr. 20, 2020, with an adjusted CFR of 6.1% (CrI 5.4%–6.9%). With reporting rates of less than 50%, the adjusted CFR for the US was 1.78 (CrI 0.8%–3.6%).INTERPRETATION:Our estimates suggest that, if the reporting rate is less than 50%, the adjusted CFR of COVID-19 in Canada is likely to be less than 2%. The CFR estimates for the US were higher than those for Canada, but the adjusted CFR still remained below 2%. Quantification of case reporting can provide a more accurate measure of the virulence and disease burden of severe acute respiratory syndrome coronavirus 2.

The risk of death associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is fundamental to the disease burden imposed by the coronavirus disease 2019 (COVID-19) pandemic. Quantification of this risk can provide critical information on the health and socioeconomic impact of the pandemic and identify population subgroups at highest risk for severe outcomes. The risk of death from a diagnosed infection, often referred to as the case-fatality rate (CFR), is the proportion of people who die from a disease among all those diagnosed with the disease over a certain period.Estimates of the COVID-19 CFR vary in different populations and at different stages of the outbreak, ranging from 0.4% in China¹ to 31.4% in the northwest region of Italy.² From individual-level data for patients in Hubei Province, Mainland China,³ an adjusted CFR of 3.6% (95% confidence interval [CI] 3.6%–3.8%) was estimated. For the outbreak on the Diamond Princess cruise ship, the age-adjusted CFR was estimated at 2.6% (95% CI 0.9%–6.7%) in all age groups but was substantially higher (13.0%, 95% CI 5.2%–26.0%) among those aged 70 years or older.⁴For ongoing outbreaks and especially during the exponential growth phase, the delay between onset of disease and knowledge of the final outcome may result in biased estimates of the CFR.⁵ Furthermore, underestimation of the number of COVID-19 cases will inflate the CFR. Limited ability to test or recognize mildly or moderately symptomatic people in both the United States and Canada has likely led to substantial underestimation of the rate of infection in affected communities.^6,7Given the importance of the CFR in public health planning, we sought to estimate the CFR for ongoing COVID-19 outbreaks in the US and Canada while accounting for preferential ascertainment of severe cases (leading to underestimation) and the lag time between disease onset and death.     

Null alleles at the Huntington disease locus: implications for diagnostics and CAG repeat instability

PCR amplification of the CAG repeat in exon 1 of the IT15 gene is routinely undertaken to confirm a clinical diagnosis of Huntington disease (HD) and to provide predictive testing for at-risk relatives of affected individuals. Our studies have detected null alleles on the chromosome carrying the expanded repeat in three of 91 apparently unrelated HD families. Sequence analysis of these alleles has revealed the same mutation event, leading to the juxtaposition of uninterrupted CAG and CCG repeats. These data suggest that a mutation-prone region exists in the IT15 gene bounded by the CAG and CCG repeats and that caution should be exercised in designing primers that anneal to the region bounded by these repeats. Two of the HD families segregated null alleles with expanded uninterrupted CAG repeats at the lower end of the zone of reduced penetrance. The expanded repeats are meiotically unstable in these families, although this instability is within a small range of repeat lengths. The haplotypes of the disease-causing chromosomes in these two families differ, only one of which is similar to that reported previously as being specific for new HD mutations. Finally, no apparent mitotic instability of the uninterrupted CAG repeat was observed in the brain of one of the HD individuals.