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X-linked acrogigantism
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

X-linked acrogigantism

X-linked acrogigantism (X-LAG) is a rare genetic condition characterized by abnormally rapid growth that begins in infancy or early childhood due to pituitary gland abnormalities.

Overview

X-linked acrogigantism (X-LAG) causes children to grow much faster than their peers. While babies are typically a normal size at birth, they begin to experience rapid growth shortly thereafter. This is caused by an abnormality of the pituitary gland, located at the base of the brain, which produces hormones that regulate growth and other body functions.

Symptoms

In addition to rapid growth and increased height, individuals with X-LAG may experience:

  • Enlargement (hyperplasia) of the pituitary gland or the development of a noncancerous tumor (pituitary neuroendocrine tumor or PitNET).
  • Excessive release of growth hormone and sometimes prolactin.
  • Coarse facial features.
  • Disproportionately large hands or feet (acral enlargement).
  • Increased appetite.
  • Acanthosis nigricans, a skin condition where folds and creases become thick, dark, and velvety.

Causes & Risk Factors

X-LAG is caused by a genetic change involving a duplication of material on the X chromosome, specifically at location q26.3. The duplication of the GPR101 gene is necessary to cause the condition.

  • The GPR101 gene provides instructions for a protein whose exact function is still being studied, though it is believed to be involved in pituitary cell growth or hormone release.
  • Duplication leads to an excess of the GPR101 protein, which is linked to the development of pituitary adenomas or hyperplasia.

Inheritance

X-LAG follows an X-linked inheritance pattern:

  • Females: A duplication of one of the two copies of the GPR101 gene in each cell is sufficient to cause the disorder. These often result from new (de novo) duplications during the formation of reproductive cells.
  • Males: A duplication of the only copy of the gene causes the disorder. This often occurs via somatic mosaicism, where the change arises randomly in one cell during embryonic development, meaning only some cells carry the duplication. Other males may inherit the duplication from an affected mother.

Fathers cannot pass X-linked traits to their sons.

Frequently Asked Questions

Rapid growth in X‑linked acrogigantism typically begins within the first year of life and continues at a rate far exceeding the 95th percentile for height. It is often accompanied by early onset of puberty signs, enlarged hands or feet, and coarse facial features. If growth velocity is unusually high and persistent, a pediatric endocrinologist should evaluate for pituitary hormone excess.
Diagnosis involves measuring serum growth hormone (GH) and insulin‑like growth factor‑1 (IGF‑1) levels, followed by an oral glucose tolerance test to assess GH suppression. Imaging with MRI of the pituitary gland identifies adenomas or hyperplasia. Genetic testing for duplication of the GPR101 gene on Xq26.3 confirms the X‑linked cause.
Treatment may include somatostatin analogs (e.g., octreotide) to inhibit GH release, dopamine agonists, or GH‑receptor antagonists like pegvisomant. In some cases, transsphenoidal surgery to remove pituitary tumors is indicated. Response varies, but early intervention can normalize growth velocity and reduce long‑term complications. Regular endocrine follow‑up is essential to adjust therapy.
Routine skin examinations can detect acanthosis nigricans early; maintaining a healthy weight and using topical treatments may help. Annual MRI scans of the pituitary are recommended to monitor tumor growth. Families should also watch for signs of hypoglycemia, headaches, or visual changes, and report them promptly to the endocrinologist.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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