Distal myopathies

Overview

Distal myopathies are a group of genetically distinct, slowly progressive muscle conditions named for where they start: 'distal' means furthest from the body's centre. Unlike most muscular dystrophies, which begin around the hips, shoulders or trunk, these start in the feet, ankles, calves, and sometimes the hands. Symptoms, age of onset and inheritance all vary depending on which gene is involved, and some forms affect the heart or breathing muscles too.

Symptoms

Weakness usually starts in the feet, ankles and lower legs, sometimes the hands, and is typically symmetrical (affecting both sides equally). Weakness at the back of the leg makes it hard to rise onto tiptoes; weakness at the front causes foot drop, leading to a high-stepping walk to avoid tripping, which makes uneven ground particularly tricky. Hand involvement can affect fine tasks like doing up buttons or opening packaging, and as the condition progresses, weakness can spread toward more central muscles. Sensation in the hands and feet is usually normal — a useful distinguishing feature from nerve conditions like Charcot-Marie-Tooth disease, which can look similar at first glance.

Inheritance and cause

More than 20 genes have been linked to the different forms of distal myopathy, each affecting proteins important to muscle structure or function; naming a specific form after its gene (for example, 'ANO5-related distal myopathy') is becoming the standard approach. Well-known forms include the MYH7-related (Laing), Titin-related (Udd), TIA1-related (Welander), dysferlin-related (Miyoshi) and GNE-related (Nonaka) types, plus various myofibrillar myopathies. Some are autosomal dominant (one changed copy from an affected parent), others autosomal recessive (a changed copy from both parents).

Getting a diagnosis

A GP can refer to a neurologist, who combines the clinical picture, family history, a physical exam, a creatine kinase blood test and EMG. A leg-muscle MRI often helps confirm the diagnosis and can point toward the responsible gene. Where a family member already has a genetic diagnosis, testing can target that specific gene directly; otherwise, a gene panel testing multiple distal-myopathy genes at once is standard in the UK. A muscle biopsy is used less often now that genetic testing has improved. Depending on symptoms and the specific type, heart and breathing checks — ECG, echocardiogram, lung function tests, overnight oximetry — may also be arranged.

Management and outlook

A multidisciplinary team, usually led by a neurologist, manages care, and exactly what that involves depends on the specific type — there's no gene therapy currently available, though clinical trials are underway for some of the genes involved. Where heart or breathing muscles are affected, a cardiologist and/or respiratory specialist gets involved to monitor and arrange treatment, including medication or non-invasive ventilation.

Staying moderately active — swimming, walking, cycling — supported by physiotherapy helps maintain strength and flexibility, with proper rest and recovery afterwards. For foot drop and lower-leg weakness, orthotic devices (insoles, ankle or leg braces) improve walking safety and reduce falls; some people need a wheelchair as things progress. Occupational therapy can provide practical equipment and adaptations to make everyday life more manageable.