Anoctamin-5-related limb-girdle muscular dystrophy R12

What it is

From: Orphanet

A form of limb-girdle muscular dystrophy most often characterized by an adult onset (but ranging from 11 to 51 years) of mainly proximal lower limb weakness, with difficulties standing on tiptoes being one of the initial signs. Proximal upper limb and distal lower limb weakness is also common, as well as atrophy of the quadriceps (most commonly), biceps brachii, and lower leg muscles. Calf hypertrophy has also been reported in some cases. LGMD2L progresses slowly, with most patients remaining ambulatory until late adulthood.

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.

Distal lower limb muscle weakness · Very frequent (99-80%)

Reduced strength of the distal musculature of the legs.

Limb-girdle muscular dystrophy · Very frequent (99-80%)

Muscular dystrophy affecting the muscles of the limb girdle (the hips and shoulders).

Myalgia · Very frequent (99-80%)

Pain in muscle.

Proximal muscle weakness in lower limbs · Very frequent (99-80%)

A lack of strength of the proximal muscles of the legs.

Abnormal muscle fiber morphology · Frequent (79-30%)

Any abnormality of the skeletal muscle cell. Muscle fibers are subdivided into two types. Type I fibers are fatigue-resistant and rich in oxidative enzymes (they stain light with the myosin ATPase reaction), and type II fibers are fast-contracting, fatigue-prone, and rich in glycolytic enzymes (these fibers stain darkly). Normal muscle tissue has a random distribution of type I and type II fibers.

EMG: axonal abnormality · Frequent (79-30%)

Electromyographic (EMG) findings characteristic of axonal neuropathy, with normal or slightly decreased nerve conduction velocities, normal or slightly prolonged distal latencies, but significantly reduced motor potentials and sensory amplitudes. There may be spontaneous activity upon needle EMG studies, such as increased insertional activity, positive sharp waves, and fibrillation potentials.

EMG: myopathic abnormalities · Frequent (79-30%)

The presence of abnormal electromyographic patterns indicative of myopathy, such as small-short polyphasic motor unit potentials.

EMG: myotonic runs · Frequent (79-30%)

Spontaneous, repetitive electrical activity demonstrated by electromyography (EMG).

EMG: neuropathic changes · Frequent (79-30%)

The presence of characteristic findings of denervation on electromyography (fibrillations, positive sharp waves, and giant motor unit potentials).

Elevated circulating creatine kinase concentration · Frequent (79-30%)

The activity of creatine kinase in the blood circulation is above the upper limit of normal.

Exercise-induced myalgia · Frequent (79-30%)

The occurrence of an unusually high amount of muscle pain following exercise.

Fatty replacement of skeletal muscle · Frequent (79-30%)

Muscle fibers degeneration resulting in fatty replacement of skeletal muscle fibers

Genu recurvatum · Frequent (79-30%)

An abnormally increased extension of the knee joint, so that the knee can bend backwards.

Increased endomysial connective tissue · Frequent (79-30%)

An increased volume of the endomysium, which is a connective tissue sheath that surrounds each muscle fiber. Together, bundles of muscle fibers form a fasciculus, surrounded by another layer of connective tissue called the perimysium.

Other findings in the same source

From: Orphanet

Additional reported features include Increased variability in muscle fiber diameter (Frequent (79-30%)); Internally nucleated skeletal muscle fibers (Frequent (79-30%)); Lower limb amyotrophy (Frequent (79-30%)); Muscle fiber splitting (Frequent (79-30%)); Pelvic girdle muscle atrophy (Frequent (79-30%)); Proximal muscle weakness in upper limbs (Frequent (79-30%)); Quadriceps muscle atrophy (Frequent (79-30%)); Abnormality of the calf musculature (Frequent (79-30%)); Muscle fiber atrophy (Frequent (79-30%)); Calf muscle hypertrophy (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Adolescent; Adult; Childhood

Inheritance in the source

From: Orphanet

Autosomal recessive

Frequency and the population described

From: Orphanet

Point prevalence: Unknown; Worldwide; Class only.

Understanding the inheritance label

From: MedlinePlus Genetics

An autosomal recessive pattern usually involves disease-causing changes in both copies of a gene. Parents may each carry one altered copy without having the condition themselves. A genetic counsellor can explain carrier testing and reproductive implications using the actual laboratory findings, rather than the condition name alone.

Which doctor should you see?

The suggested department for discussing Anoctamin-5-related limb-girdle muscular dystrophy R12 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 Anoctamin-5-related limb-girdle muscular dystrophy R12. 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.