Computed tomographic findings in manifesting carriers of Duchenne muscular dystrophy

Muscle MRI in female carriers of dystrophinopathy

BACKGROUND AND PURPOSE

Duchenne muscular dystrophy carriers represent a rare condition that needs to be recognized because of the possible implications for prenatal diagnosis. Muscle biopsy is currently the diagnostic instrument of choice in sporadic patients. We wanted to verify whether muscle magnetic resonance imaging (MRI) could identify a pattern of involvement suggestive of this condition and whether it was similar to that reported in Duchenne and Becker muscular dystrophy.

METHODS

Evaluation of pelvic and lower limb MRI scans of 12 dystrophinopathy carriers was performed.

RESULTS

We found a frequent involvement of the quadratus femoris, gluteus maximus and medius, biceps femoris long head, adductor magnus, vasti and paraspinal muscles, whilst the popliteus, iliopsoas, recti abdominis, sartorius, and gracilis were relatively spared. Asymmetry was a major feature on MRI; it could be detected significantly more often than with sole clinical examination and even in patients without weakness.

CONCLUSIONS

The pattern we describe here is similar to that reported in Duchenne and Becker muscular dystrophy, although asymmetry represents a major distinctive feature. Muscle MRI was more sensitive than clinical examination for detecting single muscle involvement and asymmetry. Further studies are needed to verify the consistency of this pattern in larger cohorts and to assess whether muscle MRI can improve diagnostic accuracy in carriers with normal dystrophin staining on muscle biopsy.

Increase in fetal breech presentation in female carriers of Duchenne muscular dystrophy

Female carriers of Duchenne muscular dystrophy (DMD) may demonstrate elevated serum creatine kinase (CK) and reduction of muscle dystrophin in all muscle types. We hypothesized that decreased dystrophin in uterine or pelvic girdle musculature might affect the obstetrical performance of females heterozygous for a dystrophin mutation. We reviewed the outcome of 34 deliveries resulting in 35 children from 13 women who were mothers of males attending a muscular dystrophy clinic. Obstetrical performance was examined retrospectively by chart review and patient contact. Of 35 children, 6 (17%) were delivered in the breech position, which is a fivefold increase above the national standards for term pregnancies. Of the six infants with breech presentation, two were males affected with DMD, one was a female heterozygote, one was a male who died perinatally, and the carrier status of the other two females is unknown. Most DMD affected males (12/14) were delivered in the vertex position. Thus, it is likely that maternal, rather than fetal, muscle weakness was the significant factor in determination of fetal position at term. We speculate that subtle changes in uterine or pelvic girdle muscle tone may contribute to a higher rate of fetal breech position in carriers of the DMD gene.

A manifesting carrier of Duchenne muscular dystrophy with severe myocardial symptoms

A 42-year-old so-called manifesting carrier of Duchenne muscular dystrophy (DMD), whose first complaints were severe myocardial symptoms, is described. Immunohistochemical study using anti-dystrophin anti-serum and analysis of cloned segments of X chromosome DNA were performed. Her two sons and one of her brothers appear to have had the same disease. She was admitted to the hospital complaining of dyspnoea, back pain and palpitations and was first diagnosed as having myocardial infarction. However, this diagnosis was excluded. The echocardiogram showed diffuse abnormalities of myocardial function. Serum enzymes were increased. Minimal weakness and decreased deep tendon reflexes were detected in her left lower extremity. Muscle biopsy revealed a small number of necrotic fibres. Immunohistochemical study using anti-dystrophin antiserum showed a mosaic pattern of the surface membrane. Analysis of cloned segments of X chromosome DNA from the patient and her son showed the XmnI(Asp) alleles of pERT 87-15 and the TaqI alleles of pERT 87-8 in both patients.

Manifesting carrier of Becker muscular dystrophy (BMD): clinical and recombinant DNA studies

We studied a Becker muscular dystrophy (BMD) family with a manifesting carrier. Proximal muscle weakness, pseudohypertrophy of the calves, significantly elevated serum creatine kinase and dystrophic alterations in the muscle biopsy were the characteristic phenotypical features of this manifesting carrier. The recombinant DNA study showed a recombinant chromosome with a crossover between pERT 87-8 and pERT J-Bir in the manifesting carrier. However, the proximal part of the short arm of her X chromosome was identical to a non-manifesting carrier (her sister) and to her affected brother. For this reason, we assumed the BMD mutation was proximal to the crossover. The dystrophin cDNA probes showed no deletion of DMD/BMD gene.