Definition

Facioscapulohumeral muscular dystrophy (FSHD) is a genetic disorder affecting the muscles of the face, shoulders, and upper arms. The term "facioscapulohumeral" comes from Latin: "facies" (face), "scapula" (shoulder blade), and "humerus" (upper arm). Muscular dystrophy refers to a rapid decline in muscle function. FSHD is characterized by increasing weakness and muscle wasting.

In FSHD, weakness initially affects the face, shoulders, and upper arms but can also extend to other muscles.

FSHD affects approximately 4 in 100,000 people and is the third most common type of muscular dystrophy after Duchenne Muscular Dystrophy, Becker Muscular Dystrophy, and Myotonic Dystrophy.

Causes

FSHD is caused by a mutation or defect in the genetic material on chromosome 4.

FSHD can be inherited from either parent but can also occur without a family history. Most individuals with FSHD inherit the condition from one parent, but in 10-30% of cases, neither parent carries the FSHD gene.

Risk Factor

A family history of FSHD increases the risk of developing the condition. FSHD occurs equally in males and females, but males are more likely to exhibit symptoms.

Symptoms

FSHD can be classified based on the age of symptom onset:

• Infantile FSHD: Symptoms can appear shortly after birth and generally involve more severe muscle weakness. It can also include hearing and vision issues and is linked to more severe DNA abnormalities.
• Adult-onset FSHD: This is more common, including FSHD that appears during adolescence, although facial muscle weakness can start in early childhood.

About 90% of FSHD cases show symptoms between the ages of 10 and 26, with muscle weakness and atrophy around the eyes, mouth, shoulders, abdomen, upper arms, and lower legs. Early symptoms often include facial or shoulder muscle weakness, which may not always be bilateral.

The severity of the condition varies greatly. Mild cases may not be noticeable until later in life, while severe cases are evident in infancy or early childhood. Some individuals may never develop symptoms.

Common symptoms include:

• Facial Muscle Weakness: Difficulty drinking with a straw, whistling, smiling, and pronouncing words due to weakened cheek muscles, as well as a depressed or angry facial expression.
• Shoulder Muscle Weakness: Causes scapular winging (protrusion of the shoulder blade) or drooping shoulders.
• Upper Arm Muscle Weakness: This leads to difficulty lifting arms above the head or throwing a ball.
• Progressive Muscle Weakness: This can extend to other body parts over decades, affecting physical activity, strength, and balance, potentially impairing walking.

Additional symptoms may include:

• Mild high-frequency hearing loss
• Retinal abnormalities
• Cardiac rhythm disturbances

These additional symptoms are rare, often unnoticed, and usually identified during health check-ups.

Diagnosis

FSHD can be diagnosed through a thorough physical examination, identification of characteristic FSHD signs, detailed personal and family medical history, and genetic testing.

Some laboratory tests may show increased levels of certain enzymes in the blood, like serum creatine kinase.

Electromyography (EMG) can be used to record the electrical activity of skeletal muscles during rest and contraction.

Muscle biopsies are generally not informative for diagnosing FSHD.

Family members of individuals with FSHD can benefit from physical examinations to detect signs and symptoms related to FSHD and genetic testing for diagnostic and family planning purposes.

Molecular genetic testing to identify chromosomal abnormalities can confirm an FSHD diagnosis.

Management

Treatment for FSHD aims to reduce symptoms and involves a multidisciplinary medical team including neurologists, orthopedists, rehabilitation specialists, ENT doctors, pulmonologists, and other specialists.

Management strategies include:

• Orthopedic and Physical Therapy: To maintain muscle flexibility, prevent muscle atrophy, and manage pain. Studies suggest that physical exercise can benefit FSHD patients.
• Assistive Devices: Such as foot orthoses for walking, and in severe cases, wheelchairs or other mobility aids.
• Speech Therapy: To improve speech and communication, especially if hearing loss or facial weakness is present.
• Surgical Interventions: For attaching the shoulder blade to the chest wall to stabilize it and improve upper arm movement.

Regular monitoring may involve:

• Pulmonary function tests to assess lung capacity and evaluate breathing, particularly during sleep.
• Eye exams for retinal issues in severe cases.
• Hearing tests for children and some adults.

Complications

The progression of FSHD is usually slow and rarely affects the heart or respiratory system. Most people with FSHD have a normal lifespan.

Severe FSHD can lead to:

• Foot Drop: Due to lower leg weakness, affecting walking and increasing fall risk.
• Hip and Pelvic Muscle Weakness: Causing difficulty with stairs and long-distance walking.
• Lumbar Lordosis: Excessive inward curvature of the lower spine due to abdominal muscle weakness.

Prevention

FSHD cannot be entirely prevented or cured, but certain lifestyle habits can help prevent complications, such as maintaining a nutritious diet and regular exercise.

When to see a doctor?

Consult a doctor if you experience FSHD symptoms. Genetic counselling is recommended for couples with a family history of FSHD who are planning to have children.

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