Rubinstein–Taybi syndrome

Rubinstein–Taybi syndrome is a rare genetic disorder associated with distinctive facial features, broad thumbs and toes, short stature, and developmental disability. It usually results from changes affecting the CREBBP or EP300 gene.

CREBBP: CREBBP is a gene that encodes the transcriptional coactivator CREB-binding protein, which helps regulate gene expression. Variants affecting this gene account for most diagnosed cases.
CREB-binding protein: CREB-binding protein is a transcriptional coactivator that helps coordinate gene expression and modifies chromatin. It is the protein encoded by CREBBP and a major target of disease-causing variants.
Genetic testing: Genetic testing analyzes DNA to identify variants associated with inherited or acquired conditions. Testing CREBBP and EP300 can confirm a suspected diagnosis.
Broad thumb: A broad thumb is an unusually wide thumb, sometimes accompanied by a broad great toe. Broad thumbs and great toes are characteristic physical findings.
EP300: EP300 is a gene that encodes the transcriptional coactivator p300, which regulates gene expression. Variants affecting this gene cause a smaller share of cases.
P300: P300 is a transcriptional coactivator and histone acetyltransferase encoded by EP300. It performs overlapping gene-regulatory functions with CREB-binding protein.
Clinical genetics: Clinical genetics applies genetic knowledge to diagnosis, risk assessment, and care of individuals and families. Clinical geneticists evaluate the syndrome and explain its inheritance and testing results.
Microcephaly: Microcephaly is a head size substantially smaller than expected for age and sex. It is among the findings that may accompany the syndrome.
Haploinsufficiency: Haploinsufficiency occurs when one functional copy of a gene does not produce enough product for normal function. Reduced CREBBP or EP300 activity is a central disease mechanism.
Histone acetylation: Histone acetylation is the addition of acetyl groups to histone proteins, often associated with accessible chromatin and active transcription. Both affected coactivators can modify histones, linking variants to altered gene expression.

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Cornelia de Lange syndromeCompared with: Its limb and developmental findings may resemble aspects of Cornelia de Lange syndrome.