LAMA2-related muscular dystrophy

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

LAMA2-related muscular dystrophy is a disorder that causes weakness and wasting (atrophy) of muscles used for movement (skeletal muscles). This condition varies in severity, from a severe, early-onset type to a milder, late-onset form.

Early-onset LAMA2-related muscular dystrophy is apparent at birth or within the first few months of life. It is considered part of a class of muscle disorders called congenital muscular dystrophies and is sometimes called congenital muscular dystrophy type 1A. Affected infants may have severe muscle weakness, lack of muscle tone (hypotonia), little spontaneous movement, and joint deformities (contractures). Weakness of the muscles in the face and throat can result in feeding difficulties and an inability to grow and gain weight at the expected rate. Respiratory insufficiency, which occurs when muscles in the chest are weakened, causes a weak cry and breathing problems that can lead to frequent, potentially life-threatening lung infections.

As affected children grow, they often develop an abnormal, gradually worsening side-to-side curvature of the spine (scoliosis) and inward curvature of the back (lordosis). Children with early-onset LAMA2-related muscular dystrophy often do not develop the ability to walk. Difficulty with speech may result from weakness of the facial muscles and an enlarged tongue. Seizures occur in about a third of individuals with early-onset LAMA2-related muscular dystrophy; rarely, heart complications occur in this form of the disorder.

Symptoms of late-onset LAMA2-related muscular dystrophy become evident later in childhood or adulthood, and are similar to those of a group of muscle disorders classified as limb-girdle muscular dystrophies. In late-onset LAMA2-related muscular dystrophy, the muscles most affected are those closest to the body (proximal muscles), specifically the muscles of the shoulders, upper arms, pelvic area, and thighs. Children with late-onset LAMA2-related muscular dystrophy sometimes have delayed development of motor skills such as walking, but generally achieve the ability to walk without assistance. Over time, they may develop rigidity of the back, joint contractures, scoliosis, and breathing problems. However, most affected individuals retain the ability to walk and climb stairs.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

As its name suggests, LAMA2-related muscular dystrophy is caused by mutations in the LAMA2 gene. This gene provides instructions for making a part (subunit) of certain members of a protein family called laminins. Laminin proteins are made of three different subunits called alpha, beta, and gamma. There are several forms of each subunit, and each form is produced from instructions carried by a different gene. The LAMA2 gene provides instructions for the alpha-2 subunit. This subunit is found in the laminin 2 protein, also known as merosin; it is also part of another laminin protein called laminin 4.

Laminins are found in an intricate lattice of proteins and other molecules that forms in the spaces between cells (the extracellular matrix). Laminin 2 and laminin 4 play a particularly important role in the skeletal muscles. The laminins attach (bind) to other proteins in the extracellular matrix and in the membrane of muscle cells, which helps maintain the stability of muscle fibers.

Most LAMA2 gene mutations that cause the severe, early-onset form of LAMA2-related muscular dystrophy result in the absence of functional laminin alpha-2 subunit. Mutations that cause the milder, later-onset form usually result in a reduction (deficiency) of functional laminin alpha-2 subunit. Deficiency or absence of the laminin alpha-2 subunit results in a corresponding lack of laminin 2 and laminin 4, reducing the strength and stability of muscle tissue and leading to the signs and symptoms of LAMA2-related muscular dystrophy.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

The prevalence of LAMA2-related muscular dystrophy is estimated at between 1 in 50,000 and 1 in 400,000 individuals worldwide. This condition is thought to be the most common type of congenital muscular dystrophy, accounting for between 30 and 40 percent of total cases.

Which doctor should you see?

The suggested department for discussing LAMA2-related muscular dystrophy 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 LAMA2-related muscular dystrophy. 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.