Overview
Left isomerism, also called left atrial isomerism or polysplenia syndrome, is a rare condition where the body's internal organs do not develop in their normal left-right arrangement. In a typical body, the heart, lungs, stomach, liver, and spleen are each positioned on a specific side. In left isomerism, both sides of the body develop as if they were the left side. This means a person may have multiple small spleens (called polysplenia) instead of one, and the heart and other organs may be arranged in unusual ways. The heart is almost always affected. Common heart problems include holes between the heart's chambers, abnormal connections of the large blood vessels, and issues with the heart's electrical system that controls the heartbeat. The lungs may also look different, and the digestive organs like the intestines and liver can be positioned abnormally. Some people also have problems with bile ducts in the liver. Symptoms can range from mild to very serious depending on how the heart and other organs are affected. Some babies are diagnosed before birth through ultrasound, while others are found to have the condition shortly after birth due to heart or breathing problems. Treatment focuses on correcting heart defects through surgery and managing complications in other organs. With early diagnosis and careful medical care, many children with left isomerism can do well, though ongoing monitoring is essential throughout life.
Also known as:
Key symptoms:
Multiple small spleens instead of one normal spleenHeart defects such as holes between heart chambersAbnormal positioning of the heart within the chestIrregular or very slow heartbeat (heart rhythm problems)Bluish skin color due to low oxygen levels (cyanosis)Breathing difficulties, especially in newbornsLiver positioned in the middle of the abdomen instead of the right sideIntestines that are twisted or positioned abnormallyBile duct problems that can affect liver functionStomach positioned on the wrong side of the bodyFatigue and poor feeding in infantsSwelling due to heart failure in some cases
Multifactorial
Caused by a mix of several genes and environmental factors
Neonatal
Begins at or shortly after birth (first 4 weeks)
FDA & Trial Timeline
10 eventsAnxo Pharmaceutical Co., Ltd. — PHASE1
Stanford University — NA
University of California, San Francisco
Bristol-Myers Squibb — PHASE1
Mapi Pharma Ltd. — PHASE1, PHASE2
Shionogi — PHASE1
Medicines for Malaria Venture — PHASE1
Vanda Pharmaceuticals — PHASE3
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Left isomerism.
View clinical trials →Clinical Trials
View all trials with filters →No actively recruiting trials found for Left isomerism at this time.
New trials open frequently. Follow this disease to get notified.
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 Left isomerism.
Community
No community posts yet. Be the first to share your experience with Left isomerism.
Start the conversation →Latest news about Left isomerism
Disease timeline:
New recruiting trial: Randomized Withdrawal Study in Patients With Schizophrenia
A new clinical trial is recruiting patients for Left isomerism
New recruiting trial: A Study to Evaluate the Dose Levels, Safety, and Drug Levels of Single KarXT Intramuscular Injection in Participants With Schizophrenia
A new clinical trial is recruiting patients for Left isomerism
New recruiting trial: Single Ascending Dose Study to Assess the Safety, Tolerability and Pharmacokinetics of LAI MMV055 Alone and in Combination With MMV371 in Healthy Participants
A new clinical trial is recruiting patients for Left isomerism
New recruiting trial: A Clinical Trial to Assess Pharmacokinetic Profiles, Safety and Tolerability of IVL3004 and IVL4002 in Healthy Male Subjects.
A new clinical trial is recruiting patients for Left isomerism
New recruiting trial: Study of S-892216 Long-acting Injectable (LAI) in Healthy Adult Participants
A new clinical trial is recruiting patients for Left isomerism
New recruiting trial: Predictors of Health Service Utilizations Among Key Population in Washington DC
A new clinical trial is recruiting patients for Left isomerism
New recruiting trial: Pharmacokinetics, Safety, Tolerability and Efficacy of a Subcutaneous Long-Acting Injection of Cariprazine (Cariprazine Depot) in Subjects Eligible for Treatment With Oral Cariprazine
A new clinical trial is recruiting patients for Left isomerism
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.Which specific heart defects does my child have, and what is the recommended surgical plan?,Does my child need preventive antibiotics for life, and which vaccines are most important?,Should we have genetic testing, and what does it mean for other family members or future pregnancies?,What signs of complications should prompt me to go to the emergency room immediately?,Are there any activity restrictions my child should follow?,How often will my child need cardiology and other specialist follow-up as they grow?,Are there clinical trials or specialized centers we should consider for my child's care?
Common questions about Left isomerism
What is Left isomerism?
Left isomerism, also called left atrial isomerism or polysplenia syndrome, is a rare condition where the body's internal organs do not develop in their normal left-right arrangement. In a typical body, the heart, lungs, stomach, liver, and spleen are each positioned on a specific side. In left isomerism, both sides of the body develop as if they were the left side. This means a person may have multiple small spleens (called polysplenia) instead of one, and the heart and other organs may be arranged in unusual ways. The heart is almost always affected. Common heart problems include holes betwe
How is Left isomerism inherited?
Left isomerism follows a multifactorial inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Left isomerism typically begin?
Typical onset of Left isomerism is neonatal. Age of onset can vary across affected individuals.
Which specialists treat Left isomerism?
19 specialists and care centers treating Left isomerism are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.