Is disease severity in ankylosing spondylitis genetically determined?

Area of Science:

• Rheumatology
• Medical Genetics
• Epidemiology

Background:

• Ankylosing spondylitis (AS) is a chronic inflammatory disease with a known genetic predisposition.
• Understanding the interplay between genetic and environmental factors is crucial for managing AS severity.

Purpose of the Study:

• To investigate the relative contributions of genetic and environmental factors to the severity of ankylosing spondylitis.
• To assess the heritability of disease activity and functional impairment in AS patients.

Main Methods:

• Recruited 173 families with multiple AS cases, totaling 384 affected individuals.
• Assessed disease severity using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and functional impairment via the Bath Ankylosing Spondylitis Functional Index (BASFI).
• Employed variance-components modeling and complex segregation analysis to determine genetic and environmental influences.

Main Results:

• Both disease activity (BASDAI) and functional capacity (BASFI) showed high familiality, indicating a strong genetic component.
• No significant shared environmental factors were associated with BASDAI or BASFI.
• A strong genetic correlation (0.9) between BASDAI and BASFI was observed, with significant residual heritability for each measure independently.

Conclusions:

• A major genetic contribution significantly influences ankylosing spondylitis disease severity.
• Similar to AS susceptibility, shared environmental factors play a minimal role in determining disease severity.
• Findings suggest a potential major gene influencing both disease activity and functional outcomes in AS.