Overview
Familial thrombocytosis, also known as hereditary thrombocytosis or familial essential thrombocythemia, is a rare inherited blood disorder in which the body produces too many platelets. Platelets are tiny blood cells that help your blood clot when you have a cut or injury. In this condition, the platelet count stays persistently high — often well above the normal range — not because of another illness, but because of a change (mutation) in a gene that controls how blood cells are made in the bone marrow. Having too many platelets can cause the blood to clot too easily, which raises the risk of blood clots forming inside blood vessels. These clots can block blood flow to the brain, heart, or other organs. At the same time, some people with very high platelet counts can paradoxically experience unusual bleeding. Symptoms can include headaches, dizziness, tingling in the hands and feet, and in more serious cases, strokes or heart attacks. Treatment focuses on reducing the risk of dangerous clots. Doctors may recommend low-dose aspirin to thin the blood, and in higher-risk patients, medications that lower the platelet count such as hydroxyurea or anagrelide may be used. The condition is lifelong, but with careful monitoring and treatment, many people live relatively normal lives.
Also known as:
Key symptoms:
Abnormally high platelet count found on blood testsHeadachesDizziness or lightheadednessTingling or burning sensation in the hands and feetRedness and warmth in the hands or feetUnusual fatigueBlood clots in veins or arteriesEasy bruising or unusual bleedingEnlarged spleen causing discomfort in the upper left abdomenVision changes or temporary vision loss
Clinical phenotype terms (24)— hover any for plain English
Autosomal dominant
Passed on from just one parent; each child has about a 50% chance of inheriting it
Variable
Can begin at different ages, from infancy through adulthood
FDA & Trial Timeline
1 eventData sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Familial thrombocytosis.
1 clinical trialare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →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 Familial thrombocytosis.
Community
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Start the conversation →Latest news about Familial thrombocytosis
Disease timeline:
New recruiting trial: Molecular Biology of Polycythemia and Thrombocytosis
A new clinical trial is recruiting patients for Familial thrombocytosis
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 gene mutation is causing my condition, and what does that mean for my family members?,What is my personal risk level for blood clots, and how will you decide on my treatment plan?,Should my children or siblings be tested for this condition?,What symptoms should prompt me to go to the emergency room immediately?,Are there any activities, medications, or foods I should avoid?,How often do I need blood tests and check-ups?,If I want to become pregnant, what special precautions do I need to take?
Common questions about Familial thrombocytosis
What is Familial thrombocytosis?
Familial thrombocytosis, also known as hereditary thrombocytosis or familial essential thrombocythemia, is a rare inherited blood disorder in which the body produces too many platelets. Platelets are tiny blood cells that help your blood clot when you have a cut or injury. In this condition, the platelet count stays persistently high — often well above the normal range — not because of another illness, but because of a change (mutation) in a gene that controls how blood cells are made in the bone marrow. Having too many platelets can cause the blood to clot too easily, which raises the risk o
How is Familial thrombocytosis inherited?
Familial thrombocytosis follows a autosomal dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
Are there clinical trials for Familial thrombocytosis?
Yes — 1 recruiting clinical trial is currently listed for Familial thrombocytosis on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat Familial thrombocytosis?
16 specialists and care centers treating Familial thrombocytosis are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.