Facioscapulohumeral Dystrophy - Causes, Types, Symptoms, Diagnosis, and Treatment

Introduction:

Skeletal muscles belong to the muscular system of the human body that travels along the skeletal framework. They are voluntary muscles controlled by the peripheral nervous system’s response to bring about movements. Generally, skeletal muscle mass is depicted as the representation of strength. Muscular dystrophy (MD) refers to the breakdown and degradation of muscle mass. The condition progresses gradually causing weakness and fragility. The severity of the condition and the degree of weakness differs between the muscles that are affected.

What Is Facioscapulohumeral Dystrophy?

Facioscapulohumeral muscular dystrophy (FSHD) is an inherited illness involving the muscles of the face, shoulder girdle, and lower limbs. The genetic factor is handed down in an autosomal dominant pattern (one gene from a parent is sufficient to cause the disease). The ailment starts on the face and spreads to other muscle groups. Apart from muscles, patients with facioscapulohumeral muscular dystrophy may present with other clinical features like high-frequency hearing loss and retinal vasculopathy (brain and eye disease).

What Are the Types of Facioscapulohumeral Dystrophy?

Literature has described two types of facioscapulohumeral muscular dystrophy.

• FSHD Type I: 95% of the cases are type I.

• FSHD Type II: The remaining 5% are type II.

The difference between type I and type II lies in gene expression. But the overall clinical features of both types remain the same.

What Are the Causes of Facioscapulohumeral Dystrophy?

The main genetic predisposition of facioscapulohumeral muscular dystrophy is from the alteration of the DUX4 and D4Z4 genes present on chromosomes 4 and 10.

• Hypomethylation (loss of methyl group in the chemical molecule) of the D4Z4 gene occurs in type I FSHD.

• Hypermethylation (methyl group added to the chemical molecule) of the D4Z4 gene occurs in type II FSHD.

The exact cause of methylation is not known. Normally, the DUX4 protein is expressed in reproductive cells like eggs and sperm. But the changes in methylation of D4Z4 may cause the DUX4 protein to get expressed in myocytes (muscle cells). The DUX4 proteins are destructive to muscle cells leading to cell death and muscle wasting.

What Are the Symptoms of Facioscapulohumeral Dystrophy?

Some of the clinical features of facioscapulohumeral muscular dystrophy are:

• Difficult raising the arm around the shoulder joint, especially in the side direction.

• Calf and foot muscles are majorly affected, causing an inability to lift the legs.

• The spinal involvement causes inward bending of the lower back (lumbar lordosis).

• There is no muscle contraction around the affected muscle groups. This is a unique feature of facioscapulohumeral muscular dystrophy, setting it apart from other normal muscular dystrophies.

• Facial abnormalities include lagophthalmos (incomplete closure of eyelids), a decrease in the eye-brow folds, a flat smile line, inability to wrinkle, raise or lower the eye-brows, and decreased action of the superficial muscles of the head and neck.

How to Diagnose Facioscapulohumeral Dystrophy?

The clinical features expressed by the patients will be suggestive of facioscapulohumeral muscular dystrophy. The following are the investigations recommended for diagnosing FSHD:

• Genetic Testing:

Genetic testing is considered the gold standard procedure and is attributed to accurately determining the cause of facioscapulohumeral muscular dystrophy. The test is usually performed on blood cells. This test will show changes in the DNA elements.

• Laboratory Findings:

The blood sample can show increased creatinine kinase values. The breakdown of muscles will release enormous creatinine kinase into the blood.

• Electromyography (EMG):

Electromyography will record the electrical activity of the skeletal muscle. This procedure will access muscle health and its related nerves.

• Magnetic Resonance Imaging (MRI):

Soft tissue abnormalities (like muscle issues) can be well-assessed in the radiographic image slices of magnetic resonance imaging. Fibrous tissue replacement increases water retention in the affected muscles, and fatty deposits can be seen in MRI images.

• Muscle Biopsies:

The disorganized pattern of collagen, fibrosis, and inflammatory changes can be observed in the microbiological assessment of muscle biopsy.

What Are the Treatment Options for Facioscapulohumeral Dystrophy?

Symptomatic management is the first line of treatment for facioscapulohumeral muscular dystrophy.

• Physical Therapy:

Increasing core muscle strength through rehabilitation programs should be the mainstay of care for FSHD patients.

• Orthotic Devices:

Severe diseases associated with facioscapulohumeral muscular dystrophy may not be restored well with physical therapy alone. Specialized devices like knee-ankle-foot orthoses can be designed individually for each patient to their specific needs.

• Surgical Fixation:

Scapular abnormalities (winging) can be corrected using surgical fixation. This will improve shoulder functions.

• Psychological Counseling:

Fatigue, weakness, and constant pain will emotionally distress the patients. Hence, psychotherapy and counseling would keep them in better mental well-being.

• Medication:

Painkillers and antidepressants are prescribed to alleviate the symptoms.

• Others:

Ventilatory support for hypoventilation, lubricating gels for eye dryness, laser for retinal problems, and therapies for hearing loss are the other symptom-based treatment plans for patients with facioscapulohumeral muscular dystrophy.

What Are the Differential Diagnosis for Facioscapulohumeral Muscular Dystrophy?

The symptoms of facioscapulohumeral muscular dystrophy may resemble genetic muscle disorders like,

• Limb-girdle Muscular Dystrophy- muscle wasting disorder.

• Subacute Necrotizing Encephalomyelopathy - a nervous disorder affecting muscles.

• Acid Maltase Deficiency- glycogen storage disease.

• Myotonic Dystrophy - degenerative muscle disease.

• Polymyositis - inflammatory muscle weakness.

However, the confusion can be avoided by standard genetic testing to differentiate between various diseases.

Conclusion:

Literature has shown various modifications in treatment strategies for facioscapulohumeral muscular dystrophy based on the interpretation of pain, psychological reasoning, and perception of illness of the patients. Many patients with facioscapulohumeral muscular dystrophy (more than 50%) will suffer from long-lasting pain that disturbs their daily activities. Some patients may also develop problems with hearing, swallowing, vision, and breathing.

However, patients must be well-educated and aware of the biopsychosocial model of treatment planning. Well-balanced, supportive care and therapy will increase the quality of a patient's life.

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