Congenital myopathy with fibre type disproportion (CFTD) is a condition that affects the muscles and is part of a group of genetic muscle conditions called congenital myopathies. These conditions are present from birth or in infancy and lead to muscle weakness.
In CFTD, weakness often affects the limbs, face, and breathing muscles. The condition is named after the typical appearance of muscle fibres under a microscope, where there is an inconsistency in the size of different muscle fibres.
CFTD symptoms can appear at birth, in infancy, or early childhood. Early signs include low muscle tone (hypotonia), floppiness, or delays in reaching motor milestones such as sitting up, crawling, and walking. The severity of CFTD and how it progresses can vary. Some may see their symptoms worsen over time, while for others, the condition remains the same or can mildly improve as they become adults.
The muscles closest to the centre of the body, such as those in the hip and shoulder areas, as well as the muscles of the spine and neck, are typically the most affected. Muscle weakness can also affect the muscles used for chewing and swallowing. This increases the risk of food or drink entering the airway and lungs (aspiration) or choking.
In severe cases, weakness can affect the face and muscles around the eyes (ophthalmoplegia). This can cause issues with eye movement and sometimes cause droopy eyelids (ptosis). People with CFTD often have distinct facial features, including a long face, a high arched palate, and crowded teeth.
People with CFTD may be born with or develop stiff joints, called contractures. They may also develop a curved lower back (lumbar lordosis) or a sideways curve of the spine (scoliosis), as weaker muscles cause imbalances in the body. Physiotherapy and using braces or other devices recommended by a doctor can help manage these issues and improve comfort and mobility.
Breathing problems can occur in people with CFTD, and these vary in severity. Weakness in the respiratory muscles can result in reduced lung capacity and a weak cough. In severe cases, shortness of breath and frequent chest infections may occur.
CFTD can also affect the heart, causing symptoms such as feeling out of breath, dizziness, palpitations, and chest tightness or pains. Some people may have cardiomyopathy, a heart condition that affects the heart’s ability to pump blood around the body effectively, especially if they have changes in the ACTA1 or TTN genes.
CFTD is linked to changes in several genes, including ACTA1, TPM3, TPM2, RYR1, SELENON/SEPN1, TTN, and MYH7. These genes are also linked to other muscle conditions. It’s also possible that other genes causing CFTD haven’t yet been discovered.
These genes provide instructions to make proteins that are essential for muscle contraction and structure. Muscles are made up of two types of fibres, type 1 and type 2, which are usually about the same size. In people with CFTD, type 1 fibres are smaller than type 2 fibres, which causes muscle weakness.
CFTD can be inherited in different ways, depending on the specific gene change. In most cases, people inherit CFTD in an autosomal recessive pattern, which means they would need to inherit two copies of the changed gene, one from each parent, to develop the condition.
Changes in the ACTA1 gene are usually inherited in an autosomal dominant pattern, meaning a person only needs to inherit one changed gene from either parent to develop the condition. In rare cases, the condition can appear even where there is no previous family history.
For more information, see our inheritance and genetics page.
A GP can make a referral to a neurologist for testing. A neurologist is a doctor who specialises in conditions that affect the muscles and nervous system. CFTD is usually diagnosed with a physical examination and genetic testing. Genetic testing uses a blood sample to check for changes in the genes known to cause CFTD. Once the genetic change has been identified in the person affected, it’s possible to use this sequence to diagnose other people in the family and identify unaffected carriers (in case of recessive genes).
A muscle biopsy may be needed if genetic testing is inconclusive. This involves taking a small sample of muscle to examine under a microscope and look for muscle structures associated with CFTD. Because CFTD has similarities with other congenital myopathies, doctors may need to do more tests to rule out other conditions.
For more information, see our diagnosis page.
A multi-disciplinary approach is important in not only managing the condition and symptoms but in improving wellbeing too. This involves different healthcare professionals working together.
People with CFTD should have access to a multi-disciplinary healthcare team. Usually, the lead professional will be a neurologist in a specialist neuromuscular clinic. If you don’t have contact with a neurologist or specialist doctor, speak to your GP about getting access to one.
Physiotherapy and mild exercise are crucial in maintaining muscle strength and mobility. They can also help maintain breathing capacity and delay progression of scoliosis and contractures. A physiotherapist is a healthcare professional who helps manage symptoms through movement, exercise, and manual therapy. They can put together a suitable exercise plan to follow. Recommended exercises include swimming, walking, and pedalling, as these aerobic exercises can help maintain a healthy cardiovascular system and a steady weight. Before starting any new form of exercise, it’s important to discuss this with a clinician. For advice for adults, see exercising with a muscle wasting condition. Physiotherapists can also provide advice on walking aids and wheelchairs if needed.
The ability to swallow may be affected, which can cause coughing, choking, or feeling like food is stuck in the throat. This can lead to weight loss and dehydration, which may require dietary adjustments. A dietitian may suggest changes to the texture of food or recommend avoiding foods that are tough to chew and swallow. If the problem is severe, they may prescribe food supplements or suggest a procedure called a gastrostomy. This is when doctors make a small surgical opening through the abdomen and into the stomach to insert a feeding tube (also known as a PEG tube). Having this tube means that enough nutrition and hydration can be put directly into the stomach.
For people with CFTD who may have breathing problems, regular monitoring is advised. Breathing problems can range from mild to severe, depending on the person. Weakness in the muscles that help with breathing can cause issues with breathing, coughing, and clearing mucus and secretions. People with CFTD are more likely to get chest infections, which need to be treated with antibiotics.
Overnight sleep studies can assess breathing while sleeping and diagnose night-time breathing problems, such as nocturnal hypoventilation. This is when there are low oxygen and high carbon dioxide levels while sleeping, which can cause symptoms of morning headaches and daytime fatigue. Treating nocturnal hypoventilation involves using non-invasive ventilation (NIV) during sleep.
There is a risk of problems with the heart in people with ACTA1, TTN, and MYH7 genetic changes. If heart problems are considered likely, a cardiologist, a doctor who specialises in treating heart problems, should perform regular heart checks. This includes an electrocardiogram (ECG) and echocardiogram (ECHO).
Author: Muscular Dystrophy UK
Reviewers: Prof Laurent Servais and Dr Rajesh Madhu
Last reviewed: February 2025
Next review due: February 2028
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