Overview
X-linked acrogigantism, often called X-LAG syndrome, is an extremely rare genetic condition that causes very early and severe overgrowth in infants and young children. It is caused by extra copies (duplications) of a small region on the X chromosome that includes the GPR101 gene. This gene plays a role in controlling growth hormone release from the pituitary gland, a small gland at the base of the brain. When this gene is overactive, the pituitary gland produces far too much growth hormone and a related hormone called insulin-like growth factor 1 (IGF-1), leading to gigantism — meaning the child grows much faster and much taller than expected for their age. Symptoms typically begin in the first two years of life. Affected children show a dramatic increase in height and weight, with rapid growth that is well above normal ranges. They may also develop enlarged hands and feet, coarsened facial features, and increased appetite. The pituitary gland itself may become enlarged or develop a benign tumor called a pituitary adenoma. Treatment focuses on controlling excess growth hormone. Medications such as somatostatin analogs (like octreotide or lanreotide) and growth hormone receptor blockers (like pegvisomant) may be tried, but they often do not fully control the condition. In many cases, surgery to remove part or all of the pituitary gland is needed. Lifelong hormone replacement therapy is usually required after surgery. Early diagnosis and treatment are important to prevent complications from extreme overgrowth.
Also known as:
Key symptoms:
Extremely rapid growth in height starting in infancyVery tall stature for ageEnlarged hands and feetCoarsened or thickened facial featuresIncreased appetite and excessive hungerEnlarged pituitary gland or pituitary tumorIncreased head sizeExcessive sweatingThickened soft tissuesJoint pain or discomfortAcneAdvanced bone age on X-raysIncreased body weight
Clinical phenotype terms (36)— hover any for plain English
X-linked dominant
Carried on the X chromosome; a single copy can cause the condition
Infantile
Begins in infancy, roughly 1 month to 2 years old
Treatments
No FDA-approved treatments are currently listed for X-linked acrogigantism.
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Rare Disease Specialist
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 X-linked acrogigantism.
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Questions for your doctor
Bring these to your next appointment
- Q1.How severe is my child's growth hormone excess, and what is the best treatment approach?,Will my child need pituitary surgery, and what are the risks and benefits?,If surgery is performed, what hormone replacements will be needed for life?,How often will my child need blood tests and MRI scans for monitoring?,What are the signs of an adrenal crisis, and how should I handle an emergency?,Should other family members be tested for the GPR101 duplication?,What support is available for the emotional and social challenges my child may face?
Common questions about X-linked acrogigantism
What is X-linked acrogigantism?
X-linked acrogigantism, often called X-LAG syndrome, is an extremely rare genetic condition that causes very early and severe overgrowth in infants and young children. It is caused by extra copies (duplications) of a small region on the X chromosome that includes the GPR101 gene. This gene plays a role in controlling growth hormone release from the pituitary gland, a small gland at the base of the brain. When this gene is overactive, the pituitary gland produces far too much growth hormone and a related hormone called insulin-like growth factor 1 (IGF-1), leading to gigantism — meaning the chi
How is X-linked acrogigantism inherited?
X-linked acrogigantism follows a x-linked dominant inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does X-linked acrogigantism typically begin?
Typical onset of X-linked acrogigantism is infantile. Age of onset can vary across affected individuals.
Which specialists treat X-linked acrogigantism?
1 specialists and care centers treating X-linked acrogigantism are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.