Overview
Transient myeloproliferative syndrome (TMS), also called transient abnormal myelopoiesis (TAM) or transient leukemia of Down syndrome, is a blood disorder that occurs almost exclusively in newborns with Down syndrome (trisomy 21) or babies who carry an extra copy of chromosome 21 in some of their cells. In this condition, the bone marrow — the spongy tissue inside bones that makes blood cells — produces too many abnormal, immature white blood cells called blasts. These cells build up in the blood and can affect organs like the liver and spleen. Most babies with TMS are diagnosed in the first few weeks of life, often before or shortly after birth. Common signs include a swollen belly due to an enlarged liver or spleen, fluid buildup in the body, yellowing of the skin (jaundice), and abnormal blood counts found on routine newborn testing. Importantly, in about 80–90% of affected babies, TMS goes away on its own within the first three months of life without any treatment — this is what makes it 'transient,' meaning temporary. However, TMS is not without risk. A small number of babies become seriously ill and need treatment, and about 20–30% of children who had TMS will go on to develop a more serious blood cancer called myeloid leukemia of Down syndrome (ML-DS) within the first four years of life. Close monitoring by a specialist is essential. Treatment, when needed, may include low-dose chemotherapy. The outlook for most babies is good, especially with careful follow-up care.
Key symptoms:
Swollen belly due to enlarged liver or spleenYellowing of the skin and eyes (jaundice)Fluid buildup under the skin or in the belly (edema or hydrops)Abnormal blood counts with too many immature white blood cells (blasts)Skin rash or small red or purple spots on the skin (petechiae)Pale skin due to low red blood cell counts (anemia)Bleeding more easily than normalDifficulty breathing if fluid builds up around the lungs or heartPoor feeding or low energy in the newbornAbnormal liver function detected on blood tests
Sporadic
Usually appears on its own, not inherited from a parent
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for Transient myeloproliferative syndrome.
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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 Transient myeloproliferative syndrome.
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
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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.Does my baby need treatment right now, or can we watch and wait?,How often will my baby need blood tests, and for how long?,What signs should I watch for at home that would mean I need to call you or go to the emergency room?,What is the chance that my child will develop leukemia after TMS, and how will we monitor for it?,If my baby needs chemotherapy, what side effects should I expect and how long will treatment last?,Are there any clinical trials or research studies my baby might be eligible for?,What support resources are available for our family during this time?
Common questions about Transient myeloproliferative syndrome
What is Transient myeloproliferative syndrome?
Transient myeloproliferative syndrome (TMS), also called transient abnormal myelopoiesis (TAM) or transient leukemia of Down syndrome, is a blood disorder that occurs almost exclusively in newborns with Down syndrome (trisomy 21) or babies who carry an extra copy of chromosome 21 in some of their cells. In this condition, the bone marrow — the spongy tissue inside bones that makes blood cells — produces too many abnormal, immature white blood cells called blasts. These cells build up in the blood and can affect organs like the liver and spleen. Most babies with TMS are diagnosed in the first
How is Transient myeloproliferative syndrome inherited?
Transient myeloproliferative syndrome follows a sporadic inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Transient myeloproliferative syndrome typically begin?
Typical onset of Transient myeloproliferative syndrome is neonatal. Age of onset can vary across affected individuals.
Which specialists treat Transient myeloproliferative syndrome?
8 specialists and care centers treating Transient myeloproliferative syndrome are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.