Congenital myopathy with fibre type disproportion (CFTD)

Overview

Congenital myopathy with fibre type disproportion (CFTD) is one of the congenital myopathies — genetic conditions present from birth or infancy that cause muscle weakness. Weakness commonly affects the limbs, face and breathing muscles. The name comes from what's seen under a microscope: muscle is normally made of two broadly similar-sized fibre types, but in CFTD one type is consistently smaller than the other.

Symptoms

Signs can appear at birth, in infancy, or in early childhood — low muscle tone, floppiness, and delays reaching milestones like sitting, crawling and walking are typical early clues. How the condition develops varies a lot: some people's symptoms worsen over time, for others things stay much the same, and some even see mild improvement into adulthood.

Weakness centres on the muscles closest to the trunk — hips, shoulders, spine and neck — and can also affect chewing and swallowing, raising the risk of choking or food/drink entering the airway. In more severe cases, weakness around the eyes can affect eye movement and cause drooping eyelids; distinctive facial features (a long face, a high arched palate, crowded teeth) are common. Contractures and spinal curves — a forward curve (lordosis) or sideways curve (scoliosis) — can develop as muscle imbalance takes hold; physiotherapy and orthotic devices help manage comfort and mobility here.

Breathing problems vary in severity, from reduced lung capacity and a weaker cough through to, in severe cases, breathlessness and frequent chest infections. The heart can be affected too, especially with ACTA1 or TTN gene changes, causing breathlessness, dizziness, palpitations or chest discomfort — some go on to develop cardiomyopathy.

Inheritance and cause

CFTD is linked to several genes — ACTA1, TPM2, TPM3, RYR1, SELENON, TTN and MYH7 among the known ones, with others likely still to be identified. These genes normally provide instructions for proteins essential to muscle contraction and structure; in CFTD, the smaller of the two fibre types ends up under-sized, weakening the muscle overall.

Inheritance depends on which gene is responsible: most cases are autosomal recessive (a changed copy needed from both parents), while ACTA1-related CFTD is usually autosomal dominant (one copy is enough); rarely, there's no prior family history at all.

Getting a diagnosis

A GP refers to a neurologist, who combines a physical exam with genetic testing — a blood sample checked against the known CFTD genes. Once a family's specific genetic change is identified, the same test can confirm the diagnosis in relatives and identify unaffected carriers. A muscle biopsy is used if genetic testing doesn't give a clear answer, and further tests may follow to rule out other, similar congenital myopathies.

Management and outlook

A multidisciplinary team, usually led by a neurologist, is the standard approach — a GP can help arrange this if there's no existing specialist contact. Physiotherapy and moderate exercise (swimming, walking, cycling are commonly suggested, alongside cardiovascular benefits and weight management) help maintain strength, mobility and breathing capacity, and slow the progression of contractures and scoliosis; walking aids and wheelchairs may be recommended if needed, and it's worth discussing any new exercise with your clinical team first.

Swallowing difficulties are worth taking seriously — coughing, choking, or food sticking can lead to weight loss and dehydration, and a dietitian can advise on texture changes, supplements, or, in severe cases, a feeding tube (gastrostomy). Breathing should be monitored regularly, including with overnight sleep studies for nocturnal hypoventilation, which non-invasive ventilation can treat; chest infections are treated with antibiotics as needed. Where ACTA1, TTN or MYH7 changes are involved, a cardiologist should carry out regular heart checks, including an ECG and echocardiogram.