Overview
Sebastian syndrome is a rare inherited blood disorder that affects platelets — the tiny cells in your blood that help stop bleeding. It belongs to a group of conditions called MYH9-related disorders, which also includes May-Hegglin anomaly, Fechtner syndrome, and Epstein syndrome. These conditions were once thought to be separate diseases but are now understood to be different expressions of the same underlying genetic problem. In Sebastian syndrome, platelets are unusually large (a condition called macrothrombocytopenia) and there are fewer of them than normal. Inside certain white blood cells called neutrophils, there are small clumps of protein called inclusion bodies. These are a hallmark feature of the condition. Because platelet numbers are low, people with Sebastian syndrome may bruise easily, bleed longer than usual after cuts or injuries, and have heavy menstrual periods. Despite the low platelet count, many people with Sebastian syndrome live relatively normal lives. Serious bleeding is less common than the platelet numbers might suggest, because the large platelets can still function reasonably well. Treatment focuses on managing bleeding risk, especially before surgeries or dental procedures. There is no cure, but supportive care can help people stay safe and active.
Also known as:
Key symptoms:
Abnormally large platelets (giant platelets) seen on blood testsLow platelet count (thrombocytopenia)Easy bruisingProlonged bleeding from cuts or injuriesHeavy or prolonged menstrual periodsNosebleeds that are hard to stopInclusion bodies (protein clumps) inside white blood cells called neutrophilsBleeding after dental procedures or surgeryOccasional small red or purple spots on the skin from minor bleeding (petechiae or purpura)
Autosomal dominant
Passed on from just one parent; each child has about a 50% chance of inheriting it
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for Sebastian syndrome.
View clinical trials →Clinical Trials
View all trials with filters →No actively recruiting trials found for Sebastian syndrome 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 Sebastian syndrome.
Community
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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.What is my current platelet count and how does it affect my bleeding risk?,Do I need to take any precautions before dental work or surgery?,Should I avoid any specific medications or activities?,Is genetic testing recommended for my family members?,Are there any signs that would suggest my condition is more like Fechtner or Epstein syndrome, which can affect the kidneys and hearing?,What should I do if I have an accident or need emergency surgery?,Are there any clinical trials or new treatments I should know about?
Common questions about Sebastian syndrome
What is Sebastian syndrome?
Sebastian syndrome is a rare inherited blood disorder that affects platelets — the tiny cells in your blood that help stop bleeding. It belongs to a group of conditions called MYH9-related disorders, which also includes May-Hegglin anomaly, Fechtner syndrome, and Epstein syndrome. These conditions were once thought to be separate diseases but are now understood to be different expressions of the same underlying genetic problem. In Sebastian syndrome, platelets are unusually large (a condition called macrothrombocytopenia) and there are fewer of them than normal. Inside certain white blood cel
How is Sebastian syndrome inherited?
Sebastian syndrome follows a autosomal dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Sebastian syndrome typically begin?
Typical onset of Sebastian syndrome is neonatal. Age of onset can vary across affected individuals.
Which specialists treat Sebastian syndrome?
4 specialists and care centers treating Sebastian syndrome are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.