The genetic aspects of multiple sclerosis.

Area of Science:

• Epidemiology
• Genetics
• Environmental Health

Background:

• Multiple sclerosis (MS) exhibits significant geographical variations in prevalence.
• MS also shows substantial familial clustering, suggesting a genetic component.
• However, geographical variations could stem from genetic factors, and familial clustering from shared environments, complicating etiological interpretations.

Purpose of the Study:

• To explore the complex interplay of genetic and environmental factors in the etiology of multiple sclerosis.
• To critically evaluate the reliability of inferences drawn from geographical variation and familial clustering in MS.
• To lay the foundation for identifying specific genes and environmental factors contributing to MS.

Main Methods:

• Review of epidemiological studies on multiple sclerosis prevalence and familial aggregation.
• Analysis of methodologies used to differentiate genetic from environmental influences.
• Synthesis of evidence to understand the etiological contributions of "nature" (genetics) and "nurture" (environment).

Main Results:

• Geographical variations in MS prevalence are consistently observed.
• Familial clustering is a significant feature of MS epidemiology.
• Crude inferences linking geographical variation solely to environmental causes or familial clustering solely to genetic causes are unreliable.

Conclusions:

• The etiology of multiple sclerosis is likely multifactorial, involving both genetic predisposition and environmental exposures.
• Sophisticated epidemiological methods are essential to disentangle the contributions of genetics and environment.
• Decades of research have been built upon these epidemiological foundations to identify specific MS-related genes.