Overview
Idiopathic giant cell myocarditis (GCM) is a rare and serious inflammatory disease of the heart muscle. The word "idiopathic" means the exact cause is unknown. In this condition, the immune system attacks the heart muscle, and large cells called "giant cells" (formed by fused immune cells) are found in the heart tissue. This leads to severe inflammation and damage to the heart. The disease mainly affects young to middle-aged adults and can progress rapidly. Common symptoms include heart failure (shortness of breath, swelling in the legs, fatigue), abnormal heart rhythms (palpitations, fainting, or sudden cardiac arrest), and chest pain. Some patients may also develop blood clots. Because the heart's pumping ability can decline quickly, this condition can become life-threatening within weeks to months if not treated. Treatment typically involves strong medications that suppress the immune system, such as cyclosporine, corticosteroids, and other immunosuppressive drugs. Many patients eventually require a heart transplant. While treatment can slow the disease and improve symptoms, giant cell myocarditis remains one of the most aggressive forms of myocarditis. Early diagnosis through heart biopsy is critical because it allows doctors to start the right treatment as soon as possible. About 20-25% of patients with GCM also have another autoimmune condition, such as inflammatory bowel disease or thyroid disease.
Also known as:
Key symptoms:
Shortness of breath, especially with activity or lying downRapid or irregular heartbeat (palpitations)Chest painSevere fatigue and weaknessSwelling in the legs, ankles, or feetFainting or near-fainting episodesSudden cardiac arrestDizziness or lightheadednessInability to exercise or do normal activitiesFluid buildup in the lungsUnexplained weight gain from fluid retentionLow blood pressure
Sporadic
Usually appears on its own, not inherited from a parent
Adult
Begins in adulthood (age 18 or older)
Treatments
No FDA-approved treatments are currently listed for Idiopathic giant cell myocarditis.
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Idiopathic giant cell myocarditis.
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Caregiver Resources
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Questions for your doctor
Bring these to your next appointment
- Q1.How severe is the damage to my heart, and what is my current heart function?,What immunosuppressive medications do you recommend, and what are the main side effects?,Am I likely to need a heart transplant, and when should we start planning for that?,Should I have an implantable defibrillator (ICD) to protect against dangerous heart rhythms?,What activity restrictions should I follow, and when might I be able to return to normal activities?,How often will I need follow-up visits, biopsies, or imaging tests?,Are there any clinical trials or new treatments I should consider?
Common questions about Idiopathic giant cell myocarditis
What is Idiopathic giant cell myocarditis?
Idiopathic giant cell myocarditis (GCM) is a rare and serious inflammatory disease of the heart muscle. The word "idiopathic" means the exact cause is unknown. In this condition, the immune system attacks the heart muscle, and large cells called "giant cells" (formed by fused immune cells) are found in the heart tissue. This leads to severe inflammation and damage to the heart. The disease mainly affects young to middle-aged adults and can progress rapidly. Common symptoms include heart failure (shortness of breath, swelling in the legs, fatigue), abnormal heart rhythms (palpitations, faintin
How is Idiopathic giant cell myocarditis inherited?
Idiopathic giant cell myocarditis follows a sporadic inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Idiopathic giant cell myocarditis typically begin?
Typical onset of Idiopathic giant cell myocarditis is adult. Age of onset can vary across affected individuals.
Which specialists treat Idiopathic giant cell myocarditis?
2 specialists and care centers treating Idiopathic giant cell myocarditis are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.