Carriers Of Becker Muscular Dystrophy Research Articles

Cardiac Magnetic Resonance Depiction of Different Morphological Appearances of Becker Cardiomyopathy in Siblings

Becker muscular dystrophy (BMD) is an X-linked recessive disorder involving mutation of the dystrophin gene. Cardiac involvement in BMD is frequent and represents the foremost cause of mortality. Two male siblings with severe left ventricular (LV) dysfunction and presence of deletion in the dystrophin gene underwent cardiac magnetic resonance (CMR) imaging, which revealed typical but varying imaging findings. The CMR revealed dilated left ventricle with severe global hypokinesis with preserved right ventricular (RV) function. Few patchy areas of septal edema were seen with typical epicardial enhancement along the LV lateral wall and the RV side of septum in one sibling. Both the siblings revealed an elevated myocardial native T1 values. CMR has the potential to detect cardiac involvement early by identifying and quantifying fibrosis, before wall motion abnormalities set in and determine prognosis in patients with muscular dystrophy and BMD carriers.

Duchenne and Becker muscular dystrophy carriers: Evidence of cardiomyopathy by exercise and cardiac MRI testing

BackgroundVaried detection methods have resulted in conflicting reports on the prevalence of cardiac disease in Duchenne and Becker muscular dystrophy carriers (MDC). MethodsWe performed a prospective cohort study of 77 genetically-confirmed MDC mothers, 22 non-carrier mothers, and 25 controls. All participants underwent Cardiopulmonary Exercise Testing (CPET) and Cardiac Magnetic Resonance imaging (CMR). Results25% of carriers had ventricular ectopy in recovery of exercise (RecVE) as compared to 1 non-carrier and no controls (p = .003). No difference in age or maximal oxygen consumption was noted. 11 carriers had abnormal (<55%) left ventricular ejection fraction by CMR. Evidence of late gadolinium enhancement (LGE) was noted in 48% of MDC, 1 non-carrier patient and no control subjects (p < .0001). Subset analysis of LGE+ and LGE- subjects revealed differences in age (44.1 v 38.6 yrs.; p = .005), presence of RecVE, (38.9% v 10.5%, p = .004), and high serum creatine kinase (CK) (> 289 U/l; 52.8% v 31.6%, p = .065). ConclusionWe describe the prevalence of disease using CPET and CMR in genetically-proven MDC. 49% of carriers had fibrosis, opposed to 5% of non-carriers, highlighting the importance of genetic testing in this population. Despite cardiomyopathy, functional assessment by treadmill was normal, illustrating the discrepancy in cardiac and skeletal muscle impacts. Age, RecVE and serum CK appear to have an important role in predicting cardiomyopathy. Serum CK levels suggest that a systemic higher global disease severity and not tissue heterogeneity may be the etiology for greater cardiac disease and relatively spared skeletal muscle disease in this population.Clinical Trial Registrationhttps://clinicaltrials.gov/ct2/show/NCT02972580?term=mendell&cond=Duchenne+Muscular+Dystrophy&rank=5; ClinicalTrials.gov Identifier: NCT02972580

DUCHENNE MUSCULAR DYSTROPHY - GENETICS: P.219Duchenne and Becker muscular dystrophy carriers: emerging evidence for a clinically important cardiomyopathy

DUCHENNE MUSCULAR DYSTROPHY - GENETICS: P.219Duchenne and Becker muscular dystrophy carriers: emerging evidence for a clinically important cardiomyopathy

Skewed X-chromosome inactivation plays a crucial role in the onset of symptoms in carriers of Becker muscular dystrophy.

Becker muscular dystrophy (BMD) is an X-linked recessive disorder affecting approximately 1: 18.000 male births. Female carriers are usually asymptomatic, although 2.5-18% may present muscle or heart symptoms. In the present study, the role of the X chromosome inactivation (XCI) on the onset of symptoms in BMD carriers was analysed and compared with the pattern observed in Duchenne muscular dystrophy (DMD) carriers. XCI was determined on the lymphocytes of 36 BMD carriers (both symptomatic and not symptomatic) from 11 families requiring genetic advice at the Cardiomyology and Medical Genetics of the Second University of Naples, using the AR methylation-based assay. Carriers were subdivided into two groups, according to age above or below 50years. Seven females from the same families known as noncarriers were used as controls. A Student's t-test for nonpaired data was performed to evaluate the differences observed in the XCI values between asymptomatic and symptomatic carriers, and carriers aged above or below 50years. A Pearson correlation test was used to evaluate the inheritance of the XCI pattern in 19 mother-daughter pairs. The results showed that symptomatic BMD carriers had a skewed XCI with a preferential inactivation of the X chromosome carrying the normal allele, whereas the asymptomatic carriers and controls showed a random XCI. No concordance concerning the XCI pattern was observed between mothers and related daughters. The data obtained in the present study suggest that the onset of symptoms in BMD carriers is related to a skewed XCI, as observed in DMD carriers. Furthermore, they showed no concordance in the XCI pattern inheritance.

P4.07 Cardiac involvement in Egyptian Duchenne and Becker muscular dystrophy carriers

P4.07 Cardiac involvement in Egyptian Duchenne and Becker muscular dystrophy carriers

Pulsed doppler tissue imaging in dystrophinopathic cardiomyopathy

Cardiac dysfunction is a primary feature in patients and female carriers of Becker muscular dystrophy (BMD). Conventional echocardiography and pulsed Doppler tissue imaging (DTI) were performed in 28 patients with BMD, in 20 female carriers, and in 38 control participants (20 men and 18 women). Left ventricular ejection fraction (LVEF) was lower in BMD patients (P <.02) and carriers (P <.02) than in normal participants. Two subgroups of BMD patients were identified: A1 = LVEF ≥ 55% (n = 20) and A2 = LVEF < 55% (n = 8). The carriers displayed LVEF ≥ 55%. Compared with control participants the diastolic alterations by conventional echocardiography were lower early filling peak in the subgroup A1 (P <.05) and prolonged isovolumic relaxation time in A1, A2, and in carriers (at least P <.02). Furthermore, pulsed DTI showed lower early diastolic wave peak at basal septum in A2 (P <.05) and in carriers (P <.0001); at lateral mitral annulus and at basal inferior wall in A1, A2, and in carriers (at least P <.05); lower early/late diastolic wave ratio at basal septum and lateral mitral annulus (P <.05) in carriers; and prolonged isovolumic relaxation time in A1, A2, and in carriers (at least P <.02), except at lateral mitral annulus of carriers. Systolic parameters investigated by pulsed DTI detected lower peak systolic wave at basal septum in A1, A2, and carriers (P <.02); at lateral mitral annulus in carriers (P <.02); at basal inferior wall in A1, A2 (P <.02), and in carriers (P <.0001); and lower time-velocity integral of S wave at each segment in A1, A2, and in carriers. In dystrophinopathic cardiomyopathy, pulsed DTI may be a useful technique to assess diastolic dysfunction and appears to be a promising tool in identifying early regional systolic alterations in patients and carriers with normal LVEF. (J Am Soc Echocardiogr 2002;15:891-9.)

Signs and symptoms of Duchenne muscular dystrophy and Becker muscular dystrophy among carriers in the Netherlands: a cohort study

Carriers of Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) may show muscle weakness or dilated cardiomyopathy. Studies focusing on skeletal-muscle involvement were done before DNA analysis was possible. We undertook a cross-sectional study in a population of definite carriers to estimate the proportion and to assess the clinical profile of carriers with symptoms. We also assessed a possible correlation between genotype and phenotype. Carriers of DMD and BMD, aged 18-60 years, were traced through the files of the central register kept at the Department of Human Genetics in Leiden, Netherlands. For each carrier who agreed to participate a medical history was taken, and muscle-strength assessment by hand-held dynamometry and manual muscle testing and cardiological assessment were done. 129 carriers of muscular dystrophy (85 DMD, 44 BMD) participated in the study. In 90 women from 52 (70%) families, 37 different mutations were found. 28 (22%) women had symptoms. 22 (17%) had muscle weakness, varying from mild to moderately severe. Muscle weakness was found in carriers of DMD and BMD, but dilated cardiomyopathy was found only in seven (8%) carriers of DMD, of whom one had concomitant muscle weakness. There was an unexpectedly high proportion of left-ventricle dilation (18%). No genotype-phenotype correlation was found. Clinical manifestation of muscle weakness, dilated cardiomyopathy, or both can be found in about a fifth of carriers of DMD and BMD. If left-ventricle dilation is taken into account, the proportion of carriers with symptoms is even higher, amounting to 40%.

Dystrophin-associated protein abnormalities in dystrophin-deficient muscle fibers from symptomatic and asymptomatic Duchenne/Becker muscular dystrophy carriers

The absence of dystrophin in muscle fibers is associated with a major reduction in dystrophin-associated proteins (DAPs) and disruption of the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. We investigated the expression of the DAPs beta-dystroglycan, alpha-sarcoglycan, gamma-sarcoglycan and syntrophin as well as utrophin in the muscles of 13 Duchenne muscular dystrophy (DMD) carriers (with variable percentages of dystrophin-deficient fibers and with a range of clinical symptoms), 2 Becker muscular dystrophy (BMD) carriers (expressing a highly truncated protein in some fibers), 2 girls with a DMD-like phenotype, and 11 BMD carriers with almost normal dystrophin expression (reduced or patchy distribution in a few fibers only and rare dystrophin-deficient fibers). DAPs were highly reduced in all fibers lacking dystrophin in the DMD carriers, but were almost normal in the dystrophin-deficient fibers of the 2 BMD carriers with highly truncated dystrophin. In the 11 BMD carriers with nearly normal dystrophin, the few fibers with reduced or patchy dystrophin immunostaining also showed reduced DAP expression in correlation with dystrophin expression. Immunoblot for beta-dystroglycan and alpha-sarcoglycan confirmed the immunohistochemical findings. Utrophin expression was slightly increased in a proportion of fibers in the DMD and BMD carriers with dystrophin mosaicism. We found no correlation between utrophin expression and DAP expression. We conclude that absence or reduction of dystrophin in muscle fibers of DMD and BMD carriers causes a reduction of DAPs in the same fibers, as observed in DMD and BMD patients, while utrophin does not seem to play a role in DAP expression in adult muscle.

Sarcolemmal distribution of abnormal dystrophin in Xp21 carriers

Some Becker muscular dystrophy carriers, related to patients with specific DNA deletions, demonstrate both normal and abnormally sized dystrophin bands through qualitative Western blot analysis. The purpose of the present investigation was to assess the sarcolemmal distribution of the altered dystrophin in such carriers. Fibres expressing the normal or deleted dystrophin were identified using specific antibodies which reacted with epitopes from within the deleted region. No negative fibres or patchy immunostaining could be seen when sections from four carriers were labelled with either antibodies (C-terminal and corresponding to the deleted region), although a significant amount of abnormal dystrophin was present in their muscle (as seen on blots). Thus, we were able to confirm that in a proportion of the myonuclei, the defective allele was present on the active X chromosome. Our results suggest that the two types of nuclei were randomly distributed, resulting in normal and abnormal dystrophin molecules which were so intimately mixed that dystrophin-incompetent fibres could not be distinguished in the skeletal muscle from the Xp21 carriers.

Detection of Duchenne and Becker muscular dystrophy carriers by quantitative multiplex polymerase chain reaction analysis

We developed a method for the detection of Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) carriers. The method is based on the quantitative analysis of the products of standard multiplex polymerase chain reaction (PCR) from 18 different exons of the dystrophin gene, and is designated "QM-PCR." We detected deletions of one or more exons by standard multiplex PCR in DMD/BMD patients in 14 of 18 families examined (77.7%). The same deletions were readily demonstrated by QM-PCR in nine of 14 mothers (64.3%) and in another six of 22 possible carriers in these families. In five families where deletions were detectable in DMD/BMD patients, the mothers did not exhibit any deletions in their peripheral blood (35.7%). We obtained evidence for germinal mosaicism in at least two of these families and confirmed carrier identification by haplotype analysis using CA repeat polymorphisms at the 5' and 3' ends of the dystrophin gene. Furthermore, analysis of 17 coded DNA samples from normal females and obligatory carriers by QM-PCR showed that this technique could directly identify carriers of deletions in any of 18 different exons of the dystrophin gene. Its application in combination with existing techniques is expected to significantly improve the accuracy of carrier diagnosis in many families, and it may also be applicable to families in which pedigree and polymorphism information is insufficient for carrier diagnosis.

Dystrophin immunohistochemistry in a symptomatic carrier of becker muscular dystrophy

Immunohistochemical localization of dystrophin was studied in a symptomatic carrier of Becker muscular dystrophy (BMD). Muscle biopsy specimens from a female carrier showed findings compatible with slowly progressive muscular dystrophy by ordinary histochemical examinations. Immunohistochemical study, using an antiserum raised against a synthetic peptide fragment of dystrophin, demonstrated a mixture of staining patterns, including continuous but faint positive fibres, partially disrupted fibres and negative fibres. These findings were identical to those of patients with BMD and appear to differ from previous findings in female carriers of Duchenne muscular dystrophy. This report is the first immunohistochemical study of a symptomatic female proven by molecular genetic analysis to be a carrier of BMD.

Evaluation of carrier detection rates for Duchenne and Becker muscular dystrophies using serum creatine-kinase (CK) and pyruvate-kinase (PK) through discriminant analysis.

Serum pyruvate-kinase (PK) and creatine-kinase (CK) determinations have been carried out in a sample of 100 obligate carriers for the Duchenne muscular dystrophy (DMD) gene, 23 obligate carriers for the Becker muscular dystrophy (BMD) gene, and 50 normal adult control women. Blood samples were collected from all subjects three times on three independent occasions and the means of these three determinations were considered for both PK and CK activities in the statistical analysis. Discriminant analysis has shown that, in the group of carriers for the DMD gene, the estimated misclassification frequencies (M.F.) using either serum CK, PK, or both enzymes were: 26.5% for CK alone, 19.5% for PK alone, and 19% for both enzymes. In the group of carriers for the BMD gene, the estimated proportions of M.F. were: 31.7% for CK alone, 23.8% for PK alone, and 20.4% for both enzymes. It is concluded that, although a proportion of carries still remains undetected, the use of serum PK determinations enhances the capability of detecting carriers of both DMD and BMD mainly when compared with serum CK alone.

Becker muscular dystrophy: carrier detection by real-time ultrasound.

The applicability was tested of real-time ultrasound imaging to the high musculature for the carrier detection of Becker muscular dystrophy (BMD). A total of 17 obligate carriers were examined. Ultrasound images in 3 patients, aged between 46 and 59 years, showed moderate differences compared with the controls. In 3 other obligate carriers, aged between 46 and 71 years, only doubtfully abnormal findings could be made; ultrasound images showed no differences in 11 BMD carriers aged between 10 and 47 years. In women aged over 40 years, compared with adequate controls of the same body type, real-time ultrasound imaging may provide additional evidence and thus help in the detection of BMD carriers.

Carrier detection in Becker muscular dystrophy using creatine kinase estimation and DNA analysis.

Serum creatine kinase levels in 39 control females and 59 obligate carriers of Becker muscular dystrophy (BMD) have been used to construct likelihood ratios for carrier detection. In 24 possible carriers of BMD, analysis of DNA with X chromosome specific DNA probes linked to the dystrophy gene, has been used in conjunction with creatine kinase measurement to calculate final risk estimates of carrier status. Incorporation of information from probe genotype into the Bayesian calculation, enables a substantially lower risk to be deliniated for some possible carriers of the BMD gene. Thus, although the existing DNA probes are not sufficiently closely linked to BMD to be used in prenatal diagnosis, they can make a major contribution to genetic counseling by refining the estimated probability of carrier status.

Plasma puryvate kinase and creatine kinase activity in Becker muscular dystrophy

Plasma creatine kinase (CK) and pyruvate kinase (PK) were measured in 31 obligate carriers of Becker muscular dystrophy (BMD), 36 BMD patients and appropriate controls. Mean plasma CK was 108 U/l in obligate carriers and 62 U/l in 43 age- and sex-matched controls ( P < 0.001 carriers vs controls). Control CK reference range was 31–125 U/l (mean ± 2 SD of log transformed values). Mean plasma PK was 40 U/l in obligate carriers and 34 U/l in 56 controls ( P < 0.02 carriers vs controls). Control PK reference range was 18–61 U/l. Values of CK above the reference range upper limit were found in 13 of 31 BMD obligate carriers but only 2 showed elevated PK values. The sensitivity of CK in determining BMD carrier status, although only 42%, was markedly better than PK at 6.5%. Mean plasma CK in BMD patients was 2366 U/l, a 19-fold increase over the control value of 127 U/l ( P < 0.001 patients vs controls). Control CK reference range was 40–316 U/l. In contrast, mean plasma PK in BMD patients was 353 U/l, only 7-fold higher than the mean control value of 57 U/l ( P < 0.001 patients vs controls). Control PK reference range was 22–126 U/l. Clearly, the estimation of plasma PK as a means of determining BMD carrier status is markedly inferior to CK. Previous reports of increased sensitivity of PK compared with CK may have been due to artefactually elevated PK levels produced during sample preparation.

Genetic counseling in Becker type X-linked muscular dystrophy. II: Practical considerations.

A frequent problem of genetic counseling in Becker muscular dystrophy (BMD) is the differential diagnosis between BMD and the autosomal recessive benign limb-girdle muscular dystrophy (LGMD) if the pedigree pattern is not typical of X-linkage. In this situation, the a priori probability that a woman and her husband may be heterozygotes for LGMD can be shown to be 80 mu/a (mu = mutation rate in BMD; a = incidence ratio between BMD and LGMD). In addition, the age-corrected serum creatine kinase (CK) values of all female relatives are also important for the risk calculation of a woman being carrier of BMD.

Evaluation and detection of Duchenne's and Becker's muscular dystrophy carriers by manual muscle testing.

Manual muscle testing of mothers of patients with X-linked muscular dystrophy has demonstrated patterns of proximal muscle weakness. The degree of weakness usually has little effect on activities of daily living but can be detected by standardized "break" testing with manual stabilization of body parts, elimination of synergistic muscles, and mechanical advantage given to the patient. Manual muscle testing is a valuable adjunct to the clinical and biochemical tools available for detecting carriers.