Holt-Oram syndrome: a clinical genetic study

Area of Science:

• Genetics
• Clinical Medicine
• Human Diseases

Background:

• Holt-Oram syndrome (HOS) is a rare genetic disorder affecting limb and heart development.
• Previous studies have established its association with mutations in the TBX5 gene.
• Understanding the full clinical spectrum and inheritance patterns is crucial for diagnosis and management.

Purpose of the Study:

• To conduct a comprehensive clinical and genetic study of Holt-Oram syndrome (HOS) in the UK.
• To define the HOS phenotype and the spectrum of associated abnormalities.
• To investigate inheritance patterns, penetrance, and factors influencing disease severity.

Main Methods:

• Clinical assessment of 55 HOS cases, their parents, and siblings.
• Detailed analysis of skeletal and cardiac defects.
• Evaluation of inheritance patterns, including penetrance and anticipation.

Main Results:

• Skeletal defects exclusively affected the upper limbs, ranging from minor anomalies to severe reduction deformities, with the left radial ray more frequently involved.
• Cardiac defects were present in 95% of familial cases, including atrial septal defect (34%) and ventricular septal defect (25%), with varying severity.
• Autosomal dominant inheritance with 100% penetrance was confirmed, and anticipation was observed, with increasing severity in successive generations.

Conclusions:

• Holt-Oram syndrome presents a consistent phenotype of upper limb and cardiac abnormalities with autosomal dominant inheritance.
• The study highlights the wide spectrum of HOS manifestations and the importance of genetic counseling.
• Anticipation suggests potential genetic or epigenetic factors influencing disease progression over generations.