Clinically manifesting carriers in Duchenne muscular dystrophy

Three manifesting carriers of Duchenne muscular dystrophy were examined clinically and histologically. All had muscle weakness in the upper and lower limbs without facial muscle involvement, onset being at the ages of 35, 19 and 25 years, respectively. Pseudohypertrophy of calves was evident in all cases. Biochemical, electrocardiographic and histological observations revealed the presence of myopathy in all cases. Sex chromatin patterns were normal. Compared with the manifesting carriers previously reported by others, at least one case showed more severe histological findings which were typical of the advanced stage of Duchenne muscular dystrophy. The cardiac involvement in three cases was moderate. A possible involvement of other factors besides Lyonization influencing the development of myopathy in the carriers is suggested.     

Macroemg in manifesting carriers of Duchenne muscular dystrophy

The aim of present study was to analyse possible myopathic changes in the muscles of manifesting carriers of Duchenne Muscular Dystrophy (DMD) using concentric needle emg and macroemg methods. Our material consisted of 10 manifesting carriers aged 9-52 (mean 30 years) and 20 healthy age-matched females. Concentric needle emg (CNEMG) and macroemg was performed in biceps brachii (BB) muscle in both groups: carriers and controls. Myopathic changes were observed in BB muscle in 5 of 10 manifesting carriers using CNEMG and in all cases (10 carriers) using macroemg method. Macro electrode, which reflects total motor unit activity, i.e., the total number and size of component muscle fibres, supplies information about early myogenic lesion of the muscle. Therefore the macroemg seems to be a sensitive and useful electrophysiological diagnostic method in carriers of DMD.     

Skewed X inactivation in manifesting carriers of Duchenne muscular dystrophy

We studied X inactivation patterns in manifesting carriers of familial and sporadic Duchenne muscular dystrophy (DMD) or unaffected carriers of DMD by analysis of the methylation of Hpall sites in the first exon of the human androgen-receptor gene (HUMARA) from peripheral blood samples. Three of the four manifesting carriers, four of the five asymptomatic carriers, and 31 of the 32 female controls were heterozygous for the CAG repeat of HUMARA. All manifesting carriers showed skewed X inactivation, while all unaffected carriers showed almost symmetrical inactivation. One family studied over three generations is noteworthy because it includes two mother/daughter pairs, one an affected pair with skewed X inactivation, and the other a phenotypically normal carrier pair with random X inactivation. On the other hand, the extent of X inactivation for each X chromosome in 31 female controls was widely distributed. These data suggest that in carriers of DMD, both affected and unaffected, it is valuable to analyze the pattern of skewed X inactivation because it provides important prognostic information. Carriers of DMD with skewed X inactivation might show slowly progressive myopathy with advancing age.     

Computed tomographic findings in manifesting carriers of Duchenne muscular dystrophy

Clinical and computed tomographic (CT) findings in 3 manifesting carriers of Duchenne muscular dystrophy are reported. CT proved to be an important adjunct to the clinical examination: in all our 3 cases a decrease in density was found in various non-paretic muscles.     

Three cases of manifesting female carriers in patients with Duchenne muscular dystrophy

Duchenne muscular dystrophy usually affects males. However, females are also affected in rare instances. Approximately 8% of female Duchenne muscular dystrophy (DMD) carriers are manifesting carriers and have muscle weakness to some extent. We investigated the clinical features of 3 female patients with dystrophinopathy diagnosed by clinical, pathological, and genetic studies at our neuromuscular disease clinic. The onset age of manifesting symptoms varied (8-28 years). Muscle weakness grade varied as follows: patient 1 showed asymmetrical bilateral proximal upper and lower extremities weakness, patient 2 showed asymmetrical bilateral upper extremities weakness similar to scapulohumoral muscular dystrophy, and patient 3 had only bilateral asymmetric proximal lower extremities weakness. Two patients had familial histories of DMD (their sons were diagnosed with DMD), but the 1 remaining patient had no familial history of DMD. The serum creatine kinase level was elevated in all patients, but it was not correlated with muscular weakness. An electromyography study showed findings of myopathy in all patients. One patient was diagnosed with a DMD carrier by a muscle biopsy with an immunohistochemical stain (dystrophin). The remaining 2 patients with familial history of DMD were diagnosed by multiplex ligation-dependent probe amplification (MLPA). There were inconsistent clinical features in the female carriers. An immunohistochemical analysis of dystrophin could be useful for female carrier patients. Also, multiplex ligation-dependent probe amplification is essential for the diagnosis of a manifesting female carrier DMD in female myopathic patients because conventional multiplex PCR could not detect the duplication and is less accurate compared to MLPA.     

A survey of manifesting carriers of Duchenne and Becker muscular dystrophy in Wales

Manifesting carriers of Duchenne and Becker muscular dystrophy are uncommon but well described. Such patients are of particular importance with regard to the differential diagnosis from autosomal recessive limb-girdle muscular dystrophy. All mothers of affected males known to the Genetic Register of Muscular Dystrophy Families in Wales were contacted, and 167 out of a possible 190 were examined. It was estimated from pedigree and creatine kinase analysis that 119 out of the 167 were carriers of the Duchenne/Becker gene. Three manifesting carriers were identified, giving the proportion affected as 3/119 = 2.5%. We estimate the prevalence of manifesting carriers to be 1 in 100,000 of the female population, a figure comparable to the prevalence of autosomal recessive limb-girdle muscular dystrophy. During the period of the survey, several other women with similar clinical findings but without an appropriate family history were seen. We strongly suspect that some of these are also manifesting carriers of the Duchenne/Becker gene.     

Variable dystrophin expression in different muscles of a Duchenne muscular dystrophy carrier

The majority of Duchenne muscular dystrophy (DMD) female carriers show dystrophin immunostaining abnormalities, although a significant proportion of clinically non-manifesting carriers are normal following this analysis. We had the opportunity to study dystrophin immunostaining in two different muscles, the vastus lateralis and the rectus abdominis of a possible DMD carrier. While the vastus showed normal dystrophin immunostaining, pathological staining was detected in her rectus abdominis. These findings seem to indicate that dystrophin expression can vary in different muscle groups of a DMD carrier. The implications of these findings in DMD carrier detection and possible dystrophin function are discussed.     

Discordance of muscular dystrophy in monozygotic female twins: evidence supporting asymmetric splitting of the inner cell mass in a manifesting carrier of Duchenne dystrophy.

In 1990, Richards et al. reported dramatically skewed lyonization in a set of female monozygotic twins heterozygous for Duchenne muscular dystrophy (DMD). The skewed inactivation pattern was symmetrical in opposite directions, one twin being affected with DMD, the other one being normal. Here, we report an additional set of female monozygotic twins heterozygous for a mutation at the dystrophin locus. Similarly, one shows a manifesting carrier phenotype while one is normal. However, unlike the previous report, we find a skewed X inactivation pattern only in the affected twin, while the normal twin showed a random X inactivation pattern. Our results lend considerable experimental support for the models of twinning and X inactivation recently outlined by Nance in 1990, in that these twins probably represent asymmetric splitting of the inner cell mass (ICM): The affected twin likely arose when a small proportion of the ICM split off after lyonization had occurred. In this situation, the original ICM could give rise to the normal twin with random lyonization, while the newly split cells would experience catch-up growth and lead to the affected twin. Genetic studies of this family showed that the specific dystrophin gene mutation was an exon duplication that arose sporadically in the paternally derived X chromosome.     

The value of deletion analysis for carrier detection in Duchenne muscular dystrophy (DMD)

We performed genetic analysis for carrier detection for several at-risk females in a four-generation Duchenne muscular dystrophy (DMD) pedigree using deletion analysis. We demonstrated that dosage analysis is a suitable alternative method to determine the carrier status of female relatives of DMD patients shown to have a deletion within the DMD gene. Subsequently, we diagnosed an affected male fetus for an at-risk female shown to be a DMD carrier by deletion analysis. The usefulness of deletion and linkage analysis are compared. In this family, linkage analysis was complicated by the unavailability of key family members, two recombination events and by previously undisclosed nonpaternity. We found that dosage analysis was more efficient than linkage for carrier evaluation in this family.     

Childhood onset of left ventricular dysfunction in a female manifesting carrier of muscular dystrophy

Duchenne muscular dystrophy and Becker muscular dystrophy are X-linked disorders that result from a mutation in the dystrophin gene that reduces the production or effectiveness of the protein dystrophin. These disorders are clinically characterized by progressive muscle degeneration. Manifesting female carriers are generally not identified as such until after puberty, when symptoms such as muscle weakness may arise. This clinical report describes a female manifesting carrier who started to show deterioration of left ventricular systolic function, but no marked skeletal muscle weakness, at the age of 10 years. The patient's cardiac function improved significantly after dual drug therapy with an ACE inhibitor (enalapril) and a beta-blocker (carvedilol). Our case adds to the existing evidence that left ventricular myocardial dysfunction may occur during childhood in female carriers of dystrophinopathies.     

Echinogenic action of L-alpha-lysophosphatidylcholine in Duchenne muscular dystrophy: a study on carrier detection

The percentage of echinocytes induced after red cell treatment with L-alpha-lysophosphatidylcholine in the blood of 16 patients affected by Duchenne muscular dystropy (DMD) has been evaluated. Moreover, 15 mothers, 10 sisters, and 15 fathers were also included in the study. We found an increased level of echinocytes in dystrophic patients and in known and possible carriers. Correlations were also evaluated between echinocytes and serum enzymes used in DMD diagnosis, showing an increase of echinocytes also in DMD carriers with normal levels of serum creatine kinase, lactate dehydrogenase, and aldolase. Our results suggest that the sensitivity of erythrocytes to L-alpha-lysophosphatidylcholine in DMD could be used as a diagnostic test for carrier detection.     

Electromyographic pattern in Duchenne and Becker muscular dystrophy. Part II. Electromyographic pattern in Becker muscular dystrophy in comparison with Duchenne muscular dystrophy

BACKGROUND: The aim of this study was to compare the electromyographic pattern in Becker muscular dystrophy (BMD) with that found in Duchenne muscular dystrophy (DMD). MATERIAL AND METHOD: Fourteen men with BMD and 51 boys with DMD were investigated. Proximal muscles were examined: m. biceps brachii (BB) and m. rectus femoris (RF). They were divided according to the clinical criteria in two groups: of those with slight changes (group AB) and of those with severe abnormalities (CD). As in the Part I of the paper our own method of Functional-QEMG was applied in the CNEMG examination. RESULTS AND CONCLUSIONS: Spontaneous activity (fibrillations, complex repetitive discharges) was equally frequent in BMD and DMD. Linked potentials were rather frequent in either group. Myopathic features such as MUAPs low amplitude and area, polyphasic shape were seen in either condition, but more marked in DMD than in BMD. Evaluation of IP recordings revealed that IP amplitude (amplitude size) is low in DMD already at the early stage of lesion but normal or only slightly diminished in BMD. It might perhaps suggest different degrees of lesion in type II MUs between the compared types of muscular dystrophy.     

The effects of genetic counselling in Duchenne muscular dystrophy

The results of a follow-up study are presented of 53 women referred for genetic counselling between 1965 and 1969 in families with Duchenne muscular dystrophy. On the basis of pedigree data and serum levels of creatine kinase, 41 were considered to be at high risk (greater than 1 in 10), 5 at medium risk (1 in 10 to 1 in 20), and 7 at low risk (less than 1 in 20) of having an affected son or carrier daughter. In the high risk group only two were undeterred from pregnancy but one of these has subsequently been sterilized, two opted for selective abortion. Four women at high risk of having an affected son were actually pregnant at the time they were referred for counselling. The need for expert contraceptive advice is emphasized and follow-up of such families proved important for support and to discuss developments such as selective abortion.