Overview
Caudal regression-sirenomelia spectrum is a rare condition that affects the development of the lower part of the body before birth. It includes a range of problems, from mild underdevelopment of the lower spine and pelvis to the most severe form called sirenomelia (sometimes called 'mermaid syndrome'), where the legs are fused together. The condition happens when the lower part of the baby's body does not form properly during the first few weeks of pregnancy. The spectrum covers many different levels of severity. Some babies are born with only mild problems in the lower spine or sacrum (the triangular bone at the base of the spine). Others may have more serious issues, including missing or fused vertebrae, problems with the kidneys, bladder, or bowel, and abnormalities of the legs and feet. In sirenomelia, the legs are joined and the internal organs in the lower belly are often severely affected. Treatment depends on how severely a child is affected. There is no cure, but a team of specialists can help manage symptoms, support development, and improve quality of life. Surgery, physical therapy, and assistive devices are often part of long-term care. The outlook varies widely depending on the severity of the condition and which organs are involved.
Key symptoms:
Missing or underdeveloped lower spine and sacrum (tailbone area)Fused or abnormally shaped legs (in sirenomelia)Weakness or paralysis of the legsMissing or malformed kidneysBladder and bowel problems, including inability to control urination or bowel movementsAbnormal or absent genitalsHip and leg bone abnormalitiesShortened or absent lower limbsSpinal cord problemsDigestive tract abnormalitiesBreathing difficulties in severe casesClubfoot or other foot deformities
Multifactorial
Caused by a mix of several genes and environmental factors
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for Caudal regression-sirenomelia spectrum.
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Specialists
View all specialists →No specialists are currently listed for Caudal regression-sirenomelia spectrum.
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 Caudal regression-sirenomelia spectrum.
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.Which organs and body parts are affected in my child's case, and how severe is it?,What specialists does my child need to see, and how often?,What surgeries might my child need, and when?,How can we best manage bladder and bowel problems at home?,What therapies (physical, occupational, speech) would help my child most?,Are there any genetic tests we should have, and what would the results mean for future pregnancies?,What support services and patient organizations are available to help our family?
Common questions about Caudal regression-sirenomelia spectrum
What is Caudal regression-sirenomelia spectrum?
Caudal regression-sirenomelia spectrum is a rare condition that affects the development of the lower part of the body before birth. It includes a range of problems, from mild underdevelopment of the lower spine and pelvis to the most severe form called sirenomelia (sometimes called 'mermaid syndrome'), where the legs are fused together. The condition happens when the lower part of the baby's body does not form properly during the first few weeks of pregnancy. The spectrum covers many different levels of severity. Some babies are born with only mild problems in the lower spine or sacrum (the t
How is Caudal regression-sirenomelia spectrum inherited?
Caudal regression-sirenomelia spectrum follows a multifactorial inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Caudal regression-sirenomelia spectrum typically begin?
Typical onset of Caudal regression-sirenomelia spectrum is neonatal. Age of onset can vary across affected individuals.