Whole-Body Skeletal Muscle MRI Patterns in Female Dystrophinopathy Carriers

Dystrophinopathies are X-linked recessive diseases caused by pathogenic variants in the Duchenne muscular dystrophy (DMD) gene. Some women carrying a single DMD pathogenic variant manifest variable levels of symptomatology. Those who manifest severe and early-onset symptoms are considered to be affected by dystrophinopathy rather than carriers. The aim of this study was to characterize and compare muscle structure between female DMD carriers who were asymptomatic at the time of the study and female control participants using whole-body MRI (WB-MRI) and correlate the findings with clinical and genetic data.

We conducted a cross-sectional observational study comparing a group of female carriers of DMD pathogenic variants and a group of healthy noncarrier controls. The first group included obligate and genetically confirmed DMD female carriers, not classified as having dystrophinopathy. Women in the healthy group had no family history of DMD or other muscular dystrophies. All individuals underwent WB-MRI, which was evaluated using qualitative grading scales to assess muscle edema, trophism, and fatty infiltration. Neurologic examinations, serum creatine kinase measurement, DMD genetic screening, and X-chromosome inactivation studies were performed on the DMD carriers.

The study included 29 DMD female carriers and 30 healthy noncarrier controls. All DMD carriers showed signs of muscle involvement on MRI, revealing a larger proportion of skeletal muscle involvement in carriers than in controls (85% vs 27% of 48 examined muscles/group of muscles, p < 0.001). Edema, fatty infiltration, and atrophy were more common in DMD carriers (62.5% vs 8%; 81% vs 35%; and 81% vs 25%, respectively, all p < 0.001), particularly in muscles of the calves, thighs, and pelvic region. The most frequently affected muscles were gastrocnemius, gluteus maximus, and soleus. No correlations were found between the MRI results and the clinical and genetic data.

Our findings indicate that DMD female carriers who are asymptomatic at the time of our study may be at risk of developing muscle symptoms at a future time. Multidisciplinary surveillance of DMD female carriers will facilitate early detection and management of complications.