Fiber type disproportion, congenital

Congenital Fiber Type Disproportion (CFTD) is a rare and inherited muscle disorder that affects the skeletal muscles from birth. It is characterized by a significant disproportion in the size of type 1 and type 2 muscle fibers, with type 1 fibers being abnormally small compared to type 2 fibers without significant changes in the number of fibers of each type. This condition is often associated with muscle weakness, reduced muscle tone (hypotonia), and developmental delays in motor skills such as walking. The severity of symptoms can vary widely among affected individuals.

Causes

CFTD is primarily considered a genetic disorder, although the exact cause can vary. It has been linked to mutations in several genes, including the RYR1 gene and the SEPN1 gene, among others. These genes are involved in muscle function and development. The condition is inherited in an autosomal dominant or autosomal recessive pattern, depending on the specific gene mutation.

Symptoms

The primary symptom of CFTD is muscle weakness, which is present from birth or early infancy. Affected individuals may also exhibit:

• Delayed motor milestones, such as sitting, standing, and walking
• Hypotonia or reduced muscle tone
• Breathing difficulties due to weak respiratory muscles
• A high-arched palate
• Scoliosis or curvature of the spine

Diagnosis

Diagnosis of CFTD involves a thorough clinical evaluation, family history, and specialized tests. A muscle biopsy is the key diagnostic test, where a small sample of muscle tissue is examined under a microscope to identify the disproportion in fiber sizes. Genetic testing may also be conducted to identify specific gene mutations associated with the condition.

Treatment

There is no cure for CFTD, and treatment focuses on managing symptoms and improving quality of life. Treatment options may include:

• Physical therapy to strengthen muscles and improve mobility
• Occupational therapy to assist with daily activities and independence
• Respiratory support for individuals with breathing difficulties
• Orthopedic interventions for skeletal abnormalities such as scoliosis

Prognosis

The prognosis for individuals with CFTD varies. While some may experience only mild symptoms and lead relatively normal lives, others may face significant physical challenges. Early intervention and supportive care can help manage symptoms and improve outcomes.

See Also

• Muscular dystrophy
• Myopathy
• Genetic disorder