Kyle was urgently admitted to hospital at 2 years of age with rapidly progressive muscle weakness. After a bout of gastroenteritis, his parents noted that his walking became increasingly unsteady. Within two days he was unable to walk or sit unsupported. Numerous investigations ruled out the usual causes of acute muscle weakness.

The remarkable thing about Kyle was his family history. His grandfather and seven of his male cousins had all had similar episodes of weakness, lasting for weeks or months at a time, following viral infections. Because this appeared to be a (new) familial muscle disease, we visited and examined over 40 members of the family and performed a detailed genetic study. As a result we localised the gene responsible for this new hereditary muscle disorder, which we have called Episodic Muscle Weakness on the X chromosome (EMWX). Most recently, we have identified a gene mutation in affected family members. This mutation affects their ability to generate and use energy in muscle and other body tissues. We are now conducting detailed studies of muscle energy metabolism in this family.

Kyle slowly recovered from his severe weakness and got back to his normal active self. Some of his relatives have had more persistent difficulty with muscle weakness, increased muscle tone and tremor. On completion of our functional studies we are planning to commence trials of specific therapies to prevent or ameliorate episodic muscle weakness in this family.

© The Institute for Neuromuscular Research