Overview
Renal dysplasia-megalocystis-sirenomelia syndrome is an extremely rare and severe birth defect condition that combines several major abnormalities present at birth. The name describes its three main features: renal dysplasia (where the kidneys do not develop properly), megalocystis (an abnormally enlarged bladder), and sirenomelia (a condition sometimes called 'mermaid syndrome' where the legs are fused together to varying degrees). Sirenomelia occurs when the lower body does not form correctly during early pregnancy, and it often comes along with serious problems in the kidneys, urinary tract, lower spine, and other organs. Babies born with this syndrome typically have life-threatening complications because the kidneys and urinary system are severely affected. The fused or malformed lower limbs also indicate major disruptions in how blood vessels and tissues developed in the lower half of the body. Other abnormalities may include problems with the genitals, anus, and lower intestine. Unfortunately, this condition is almost always fatal before or shortly after birth. There is no cure or effective treatment. Medical care focuses on supportive measures and compassionate care. Prenatal ultrasound can often detect the major features of this syndrome during pregnancy, which allows families to receive counseling and prepare. Because of the extreme severity and the involvement of multiple organ systems, long-term survival has not been reported in most cases.
Also known as:
Key symptoms:
Fused legs (mermaid-like lower limbs)Abnormally large bladderKidneys that did not develop properly or are absentAbsent or malformed anusAbsent or malformed genitalsSevere lack of amniotic fluid during pregnancy (oligohydramnios)Underdeveloped lungsAbnormal lower spine or absent sacrumSingle umbilical artery instead of twoAbsent or malformed lower intestineFlattened facial features due to low amniotic fluid (Potter sequence)
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 Renal dysplasia-megalocystis-sirenomelia syndrome.
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Specialists
View all specialists →No specialists are currently listed for Renal dysplasia-megalocystis-sirenomelia syndrome.
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 Renal dysplasia-megalocystis-sirenomelia syndrome.
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Caregiver Resources
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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.How certain is this diagnosis based on the ultrasound findings?,Would additional imaging like fetal MRI provide more information?,What are the options for the remainder of this pregnancy?,Is there any chance this could happen again in a future pregnancy?,Should we have genetic testing done, and what would it tell us?,What palliative care and comfort measures will be available for our baby?,Can you connect us with grief counseling or support groups for families in similar situations?
Common questions about Renal dysplasia-megalocystis-sirenomelia syndrome
What is Renal dysplasia-megalocystis-sirenomelia syndrome?
Renal dysplasia-megalocystis-sirenomelia syndrome is an extremely rare and severe birth defect condition that combines several major abnormalities present at birth. The name describes its three main features: renal dysplasia (where the kidneys do not develop properly), megalocystis (an abnormally enlarged bladder), and sirenomelia (a condition sometimes called 'mermaid syndrome' where the legs are fused together to varying degrees). Sirenomelia occurs when the lower body does not form correctly during early pregnancy, and it often comes along with serious problems in the kidneys, urinary tract
How is Renal dysplasia-megalocystis-sirenomelia syndrome inherited?
Renal dysplasia-megalocystis-sirenomelia syndrome follows a sporadic inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Renal dysplasia-megalocystis-sirenomelia syndrome typically begin?
Typical onset of Renal dysplasia-megalocystis-sirenomelia syndrome is neonatal. Age of onset can vary across affected individuals.