Laing distal myopathy

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Laing distal myopathy is a condition that affects skeletal muscles, which are muscles that the body uses for movement. This disorder causes progressive muscle weakness that appears in childhood. The first sign of Laing distal myopathy is usually weakness in certain muscles in the feet and ankles. This weakness leads to tightening of the Achilles tendon (the band that connects the heel of the foot to the calf muscles), an inability to lift the first (big) toe, and a high-stepping walk. Months to years later, muscle weakness develops in the hands and wrists. Weakness in these muscles makes it difficult to lift the fingers, particularly the third and fourth fingers. Many affected people also experience hand tremors.

In addition to muscle weakness in the hands and feet, Laing distal myopathy causes weakness in several muscles of the neck and face. A decade or more after the onset of symptoms, mild weakness also spreads to muscles in the legs, hips, and shoulders. Laing distal myopathy progresses very gradually, and most affected people remain mobile throughout life. Life expectancy is normal in people with this condition.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in the MYH7 gene cause Laing distal myopathy. The MYH7 gene provides instructions for making a protein that is found in heart (cardiac) muscle and in type I skeletal muscle fibers. Type I fibers, which are also known as slow-twitch fibers, are one of two types of fibers that make up skeletal muscles. Type I fibers are the primary component of skeletal muscles that are resistant to fatigue. For example, muscles involved in posture, such as the neck muscles that hold the head steady, are made predominantly of type I fibers.

In cardiac and skeletal muscle cells, the protein produced from the MYH7 gene forms part of a larger protein called type II myosin. This type of myosin generates the mechanical force that is needed for muscles to contract. In the heart, regular contractions of cardiac muscle pump blood to the rest of the body. The coordinated contraction and relaxation of skeletal muscles allow the body to move.

It is unknown how mutations in the MYH7 gene cause progressive muscle weakness in people with Laing distal myopathy. Researchers have proposed that these mutations alter the structure of myosin in skeletal muscles, which prevents it from interacting with other proteins. The abnormal myosin gradually impairs the function of type I skeletal muscle fibers.

In most people with Laing distal myopathy, the signs and symptoms of the disorder are limited to weakness of skeletal muscles. Because myosin made with the MYH7 protein is also found in cardiac muscle, it is unclear why heart problems are not a typical feature of this condition.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

In most cases, an affected person inherits the mutation from one affected parent. A small percentage of cases result from new mutations in the gene. These cases occur in people with no history of the disorder in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Although Laing distal myopathy is thought to be rare, its prevalence is unknown. Several families with the condition have been identified worldwide.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Foot dorsiflexor weakness · Very frequent (99-80%)

Weakness of the muscles responsible for dorsiflexion of the foot, that is, of the movement of the toes towards the shin. The foot dorsiflexors include the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the peroneus tertius muscles.

Toe extensor amyotrophy · Very frequent (99-80%)

Atrophy of the extensor digitorum longus muscles, which mediate extension of the toes.

Abnormal mitochondria in muscle tissue · Frequent (79-30%)

An abnormality of the mitochondria in muscle tissue.

Distal muscle weakness · Frequent (79-30%)

Reduced strength of the musculature of the distal extremities.

Gait disturbance · Frequent (79-30%)

The term gait disturbance can refer to any disruption of the ability to walk.

High palate · Frequent (79-30%)

Height of the palate more than 2 SD above the mean (objective) or palatal height at the level of the first permanent molar more than twice the height of the teeth (subjective).

Minicore myopathy · Frequent (79-30%)

Multiple small zones of sarcomeric disorganization and lack of oxidative activity (known as minicores) in muscle fibers.

Myalgia · Frequent (79-30%)

Pain in muscle.

Other findings in the same source

From: Orphanet

Additional reported features include Neck muscle weakness (Frequent (79-30%)); Scoliosis (Frequent (79-30%)); Type 1 muscle fiber predominance (Frequent (79-30%)); Weakness of orbicularis oculi muscle (Frequent (79-30%)); Abnormality of the calf musculature (Frequent (79-30%)); Mildly elevated creatine kinase (Frequent (79-30%)); Progressive muscle weakness (Frequent (79-30%)); Talipes cavus equinovarus (Frequent (79-30%)); Dilated cardiomyopathy (Occasional (29-5%)); EMG: myopathic abnormalities (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Laing distal myopathy is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Laing distal myopathy. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.