Overview
Partial deletion of the long arm of chromosome 18 syndrome, also known as 18q deletion syndrome or distal 18q monosomy, is a rare chromosomal disorder caused by the loss of genetic material from the long arm (q arm) of chromosome 18. The size and location of the deletion can vary considerably among affected individuals, which leads to a wide spectrum of clinical features and severity. This condition is typically identified at birth or during early childhood based on characteristic clinical findings and confirmed through chromosomal analysis such as karyotyping, FISH, or chromosomal microarray. The syndrome affects multiple body systems. Common features include intellectual disability of variable degree, short stature, hypotonia (reduced muscle tone), hearing impairment (often due to aural atresia or stenosis of the ear canal), and characteristic facial features such as a flat midface, deep-set eyes, a carp-shaped mouth, and prominent antihelices of the ears. Congenital heart defects, foot deformities (including clubfoot), cleft palate, and abnormalities of the genitalia may also occur. Neurological features can include white matter abnormalities and delayed myelination, which may be related to haploinsufficiency of the myelin basic protein (MBP) gene located at 18q23. Growth hormone deficiency and autoimmune conditions, including juvenile rheumatoid arthritis and IgA deficiency, have also been reported. There is no cure for 18q deletion syndrome, and management is supportive and symptom-based. Treatment may include growth hormone therapy for short stature, hearing aids or surgical correction for hearing loss, cardiac surgery for congenital heart defects, orthopedic interventions, speech therapy, and special educational support. Early intervention programs and multidisciplinary care are important to optimize developmental outcomes. Genetic counseling is recommended for affected families to discuss recurrence risk and reproductive options.
Also known as:
Variable
Can be inherited in different ways depending on the underlying gene
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
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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
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Common questions about Partial deletion of the long arm of chromosome 18 syndrome
What is Partial deletion of the long arm of chromosome 18 syndrome?
Partial deletion of the long arm of chromosome 18 syndrome, also known as 18q deletion syndrome or distal 18q monosomy, is a rare chromosomal disorder caused by the loss of genetic material from the long arm (q arm) of chromosome 18. The size and location of the deletion can vary considerably among affected individuals, which leads to a wide spectrum of clinical features and severity. This condition is typically identified at birth or during early childhood based on characteristic clinical findings and confirmed through chromosomal analysis such as karyotyping, FISH, or chromosomal microarray.
At what age does Partial deletion of the long arm of chromosome 18 syndrome typically begin?
Typical onset of Partial deletion of the long arm of chromosome 18 syndrome is neonatal. Age of onset can vary across affected individuals.