362P Whole-body MRI reveals common and distinctive muscle involvement in “clinically asymptomatic” female carriers of pathogenic DMD variants

Abstract

DMD-carriers were traditionally considered asymptomatic given the X-linked recessive inheritance pattern of these diseases. Yet, it has recently been discovered that they exhibit different levels of muscle involvement.

This study aimed to characterize and compare the muscle structure on MRI of DMD-carriers and a control group. Secondly, we pursue a correlation between levels of muscle involvement and clinical manifestations, creatine kinase (CK) levels, DMD molecular alteration and X-chromosome inactivation (XCI) patterns. We enrolled 30 genetically confirmed DMD female carriers and 30 healthy non-carrier controls, BMI and age matched. All individuals underwent whole-body MRI, where semi-quantitative scales were used to assess muscle edema, trophism and fatty infiltration. Neurological examination, Serum CK measurement, DMD genetic screening, and XCI studies were only performed on the DMD-carriers. Statistically significant differences in muscle involvement were observed between DMD-carriers and the control group. Female carriers exhibited muscle affection in 33% of the 48 muscle groups analyzed, while the control group presented only the 10% affected. Most of the DMD-carriers’ implicated muscles showed mild atrophy and mild to moderate fatty infiltration. The muscles more frequently affected were gastrocnemius, gluteus maximus and soleus. No statistical correlation was found between the levels or pattern of muscle involvement on MRI and the neurological examination, CK values, type of genetic variant and XCI patterns. DMD-carriers exhibit frequent and distinctive muscle involvement patterns on MRI, questioning the conception of “asymptomatic” DMD-Carriers. These results, together with findings in other X-linked disorders, lead to a revision of the concept of asymptomatic carriers of X-linked recessive diseases and raise awareness of the need to develop best practice guidelines for the evaluation and management of these females.