Diego Cadavid, MD of Fulcrum Therapeutics explains facioscapulohumeral muscular dystrophy, a rare disabling disease characterized by progressive skeletal muscle loss. The disease generally begins with weakness in facial muscles but as the condition progresses,  shoulders, arms and trunk, and eventually the rest of the body is affected. progresses to weakness throughout the lower body.

Weakness involving the facial muscles or shoulders is usually the first symptom of this condition. Facial muscle weakness often makes it difficult to drink from a straw, whistle, or turn up the corners of the mouth when smiling. Weakness in muscles around the eyes can prevent the eyes from closing fully while a person is asleep, which can lead to dry eyes and other eye problems. For reasons that are unclear, weakness may be more severe in one side of the face than the other. Weak shoulder muscles tend to make the shoulder blades (scapulae) protrude from the back, a common sign known as scapular winging. Weakness in muscles of the shoulders and upper arms can make it difficult to raise the arms over the head or throw a ball.

The muscle weakness associated with facioscapulohumeral muscular dystrophy worsens slowly over decades and may spread to other parts of the body. Weakness in muscles of the lower legs can lead to a condition called foot drop, which affects walking and increases the risk of falls. Muscular weakness in the hips and pelvis can make it difficult to climb stairs or walk long distances. Additionally, affected individuals may have an exaggerated curvature of the lower back (lordosis) due to weak abdominal muscles. About 20% of affected individuals eventually require the use of a wheelchair.

The condition is due to mutations in the DUX4 gene. Fulcrum Therapeutics has a phase II clinical trial currently underway to test the safety and efficacy of losmapimod, a mitogen-activated protein kinase (MAPK) inhibitor, in persons with facioscapulohumeral muscular dystrophy.

To learn more about this and other rare neuromuscular disorders, visit checkrare.com/diseases/musculoskeletal-diseases/