IBS: a syndrome or many diseases?

Area of Science:

• Gastroenterology
• Genetics
• Psychiatry

Background:

• Irritable bowel syndrome (IBS) presents diverse gastrointestinal (GI) symptoms, often overlapping with other functional GI disorders (FGID).
• Significant psychiatric comorbidity exists, particularly in severe IBS cases.
• FGID show familial clustering and higher concordance in identical twins, suggesting a genetic predisposition.

Purpose of the Study:

• To explore the multifactorial etiologies of functional gastrointestinal disorders, including IBS.
• To investigate the role of genetic polymorphisms in GI sensory/motor dysfunction and psychiatric comorbidities.
• To consider the impact of infections and immune/neural pathways in FGID development.

Main Methods:

• Review of family and twin studies to assess hereditary factors in FGID.
• Analysis of potential genetic polymorphisms (adrenergic, opioidergic, serotonergic receptors, GNB3, 5-HT transporter, OPRM1, IL-4, IL-4R, TNFalpha).
• Consideration of environmental triggers like GI infections and inflammation.

Main Results:

• Genetic factors, including polymorphisms in neurotransmitter and immune-related genes, likely contribute to IBS pathophysiology.
• GI infections may initiate a cascade leading to FGID manifestation in susceptible individuals.
• Abnormalities in GI sensory and motor functions, alongside psychiatric factors, are key components.

Conclusions:

• Functional GI disorders arise from a complex interplay of genetic predisposition, environmental triggers, and altered GI function.
• Current symptom-based classifications may mask diverse underlying pathophysiologies.
• IBS is likely an umbrella term for distinct disorders, necessitating future classification based on specific etiologies.