Tubular aggregate myopathy

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Tubular aggregate myopathy is a disorder that primarily affects the skeletal muscles, which are muscles the body uses for movement. This disorder causes muscle pain, cramping, or weakness that begins in childhood and worsens over time. The muscles of the lower limbs are most often affected, although the upper limbs can also be involved. Affected individuals can have difficulty running, climbing stairs, or getting up from a squatting position. The weakness may also lead to an unusual walking style (gait). Some people with this condition develop joint deformities (contractures) in the arms and legs.

Skeletal muscles are normally made up of two types of fibers, called type I and type II fibers, in approximately equal quantities. Type I fibers, also called slow twitch fibers, are used for long, sustained activity, such as walking long distances. Type II fibers, also known as fast twitch fibers, are used for short bursts of strength, which are needed for activities such as running up stairs or sprinting. In people with tubular aggregate myopathy, type II fibers waste away (atrophy), so affected individuals have mostly type I fibers. In addition, proteins build up abnormally in both type I and type II fibers, forming clumps of tube-like structures called tubular aggregates. Tubular aggregates can occur in other muscle disorders, but they are the primary muscle cell abnormality in tubular aggregate myopathy.

ORPHANET DEFINITION A rare congenital myopathy characterized ultrastructurally by the presence of tubular aggregates in the subsarcolemmal region of the muscle fiber. It most commonly presents with slowly progressive proximal muscle weakness predominantly of the lower limbs, periodic paralysis, post-exertion muscle cramps, and muscular pain. Ocular anomalies like ophthalmoplegia or pupillary abnormalities may be associated. The intensity of the symptoms is variable, cases with normal muscle strength but myalgia or fatigue, as well as clinically asymptomatic cases have been described.

Inheritance

From: MedlinePlus Genetics, National Library of Medicine

Autosomal recessive; Autosomal dominant

Frequency in the source

From: MedlinePlus Genetics, National Library of Medicine

Reported case(s): 60.0; Worldwide. This is a published case count, not prevalence. Point prevalence: <1 / 1 000 000; Worldwide; Class only.

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.

EMG: myopathic abnormalities · Very frequent (99-80%)

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

Fatigable weakness · Very frequent (99-80%)

A type of weakness that occurs after a muscle group is used and lessens if the muscle group has some rest. That is, there is diminution of strength with repetitive muscle actions.

Fatiguable weakness of proximal limb muscles · Very frequent (99-80%)

A type of weakness of a skeletal muscle of proximal part of a limb that occurs after a muscle group is used and lessens if the muscle group has some rest. That is, there is diminution of strength with repetitive muscle actions.

Muscle fiber tubular inclusions · Very frequent (99-80%)

Unusual regions of densely packed membranous tubules known as tubular aggregates which present as membranous inclusions, derived from membranes of sarcoplasmic reticulum and mitochondria, containing miscellaneous proteins with a variety of enzymatic activities.

Muscle spasm · Very frequent (99-80%)

Sudden and involuntary contractions of one or more muscles.

Myalgia · Very frequent (99-80%)

Pain in muscle.

Centrally nucleated skeletal muscle fibers · Frequent (79-30%)

An abnormality in which the nuclei of sarcomeres take on an abnormally central localization (or in which this feature is found in an increased proportion of muscle cells).

Increased variability in muscle fiber diameter · Frequent (79-30%)

An abnormally high degree of muscle fiber size variation. This phenotypic feature can be observed upon muscle biopsy.

Type 2 muscle fiber atrophy · Occasional (29-5%)

Atrophy (wasting) affecting primary type 2 muscle fibers. This feature in general can only be observed on muscle biopsy.

When it may begin

From: MedlinePlus Genetics, National Library of Medicine

Adolescent; Adult; Childhood

Inheritance in the source

From: MedlinePlus Genetics, National Library of Medicine

Autosomal recessive; Autosomal dominant

Frequency and the population described

From: MedlinePlus Genetics, National Library of Medicine

Reported case(s): 60.0; Worldwide. This is a published case count, not prevalence. Point prevalence: <1 / 1 000 000; Worldwide; Class only.

Which doctor should you see?

The suggested department for discussing Tubular aggregate 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 Tubular aggregate 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.