Idiopathic giant cell myocarditis

What it is

From: Orphanet

A rare cardiac disease characterized by rapidly progressing myocarditis of unknown origin that may lead to progressive heart failure, heart block, ventricular arrhythmias, or sudden cardiac death. It is histologically characterized by myocardial necrosis and fibrosis with multinucleated giant cells and inflammatory cell infiltrate. Some patients have associated autoimmune disorders. It is a high-mortality risk condition and patients often require a heart transplant.

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.

Abnormal cardiac MRI · Very frequent (99-80%)

Abnormal results of a MRI for the heart.

Increased circulating troponin T concentration · Very frequent (99-80%)

An increased concentration of tropnin T in the blood, which is a cardiac regulatory protein that controls the calcium mediated interaction between actin and myosin. Raised cardiac troponin concentrations are now accepted as the standard biochemical marker for the diagnosis of myocardial infarction.

Myocardial late gadolinium enhancement · Very frequent (99-80%)

Areas of high signal intensity in magnetic resonance imaging of the heart appearing 10 to 15 minutes after injection of the intercellular contrast agent gadolinium.

Myocardial multinucleated giant cells · Very frequent (99-80%)

The presence of extremely large cells with multiple nuclei. The so-called giant cells are thought to be of macrophage origin.

Reduced left ventricular ejection fraction · Very frequent (99-80%)

A diminution of the volumetric fraction of blood pumped out of the ventricle with each cardiac cycle.

Congestive heart failure · Frequent (79-30%)

The presence of an abnormality of cardiac function that is responsible for the failure of the heart to pump blood at a rate that is commensurate with the needs of the tissues or a state in which abnormally elevated filling pressures are required for the heart to do so. Heart failure is frequently related to a defect in myocardial contraction.

Increased circulating NT-proBNP concentration · Frequent (79-30%)

The concentration of NT-proBNP (= N-terminal pro-B-type natriuretic peptide, = N-terminal prohormone of brain natriuretic peptide) in the blood circulation is above the upper limit of normal.

Myocardial fibrosis · Frequent (79-30%)

Myocardial fibrosis is characterized by dysregulated collagen turnover (increased synthesis predominates over unchanged or decreased degradation) and excessive diffuse collagen accumulation in the interstitial and perivascular spaces as well as by phenotypically transformed fibroblasts, termed myofibroblasts.

Myocardial necrosis · Frequent (79-30%)

Irreversible damage to heart tissue (myocardium) due to lack of oxygen after a heart attack (myocardial infarction).

Atrioventricular block · Occasional (29-5%)

Delayed or lack of conduction of atrial depolarizations through the atrioventricular node to the ventricles.

Autoimmunity · Occasional (29-5%)

The occurrence of an immune reaction against the organism's own cells or tissues.

Cardiogenic shock · Occasional (29-5%)

Severely decreased cardiac output with evidence of inadequate end-organ perfusion (i.e., tissue hypoxia) in the presence of adequate intravascular volume.

Elevated circulating C-reactive protein concentration · Occasional (29-5%)

The concentration of C-reactive protein in the blood circulation is above the upper limit of normal.

Elevated erythrocyte sedimentation rate · Occasional (29-5%)

An increased erythrocyte sedimentation rate (ESR). The ESR is a test that measures the distance that erythrocytes have fallen after one hour in a vertical column of anticoagulated blood under the influence of gravity. The ESR is a nonspecific finding. An elevation may indicate inflammation or may be caused by any condition that elevates fibrinogen.

Other findings in the same source

From: Orphanet

Additional reported features include Left ventricular dilatation (Occasional (29-5%)); Sudden cardiac death (Occasional (29-5%)); Ventricular tachycardia (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Adolescent; Adult; Childhood; Infancy

Inheritance in the source

From: Orphanet

Not applicable

Which doctor should you see?

The suggested department for discussing Idiopathic giant cell myocarditis is Cardiology, with a cardiologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

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.

• Is the main concern heart structure, rhythm, circulation or another cause?
• Which symptoms should change the timing of follow-up?
• How would a proposed investigation change the care plan?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Idiopathic giant cell myocarditis. 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.