Multiple sclerosis: symptoms, causes and prevalence

Multiple sclerosis is an autoimmune disease that affects the central nervous system, damaging the myelin sheaths that cover neurons. This damage, caused by inflammatory processes, interferes with the transmission of nerve impulses, slowing them down or completely blocking them. Myelin plays a crucial role in conducting electrical impulses in the brain and spinal cord, so its deterioration leads to a wide range of neurological symptoms.

While the exact cause of multiple sclerosis is not fully understood, it has been determined that a combination of genetic and environmental factors contributes to its development. In this article, we will explore the genetic basis of the disease, its prevalence, and the most common symptoms.

Prevalence of Multiple Sclerosis

Multiple sclerosis affects approximately 1.8 million people worldwide. Its prevalence varies by geographic region, being more common in countries farther from the equator. This distribution suggests that environmental factors, such as sunlight exposure and vitamin D levels, may influence the development of the disease.

Multiple sclerosis affects women more frequently than men, with a ratio of approximately 3:1. The disease typically manifests between the ages of 20 and 40, although cases have been reported in children and older adults. In addition to genetics and geography, other risk factors include viral infections (such as the Epstein-Barr virus) and smoking.

Symptoms of Multiple Sclerosis

Multiple sclerosis is an extremely heterogeneous disease, meaning that its symptoms can vary significantly among patients. Some of the most common symptoms include:

• Chronic fatigue: This is one of the most common symptoms as the disease progresses.
• Motor problems: These include weakness, spasticity, difficulty coordinating movements, and loss of balance.
• Sensory disordersThe symptoms are: tingling, numbness or abnormal sensations in different parts of the body.
• Visual disturbances: Such as blurred vision or temporary vision loss in one eye.
• Cognitive difficulties: Including memory problems, attention deficits, impaired reasoning, and slowed processing speed.
• Bladder and bowel dysfunction: Such as loss of urinary control or constipation issues.

Patients may experience relapses (acute episodes of symptoms) followed by periods of remission or have a progressive course in which symptoms worsen over time without periods of improvement.

Genetics of Multiple Sclerosis

Multiple sclerosis is a complex disease involving multiple genetic and environmental factors. Although it does not follow a simple inheritance pattern, several genes have been identified that influence susceptibility to the disease. Below are some of the most significant associated genes:

• IL2RA, IL7R, and IL12A: These genes encode different subunits of interleukin receptors that play a key role in regulating the immune response. Variants in these genes have been linked to an increased risk of developing multiple sclerosis, possibly due to alterations in the activation and differentiation of T cells (immune system cells), which are fundamental in autoimmunity.
• CD6: This gene encodes a protein expressed on the surface of T cells and other immune cells, involved in cell activation and proliferation. Variants in CD6 have been associated with susceptibility to multiple sclerosis, indicating a role in the modulation of the immune response.
• BACH2: BACH2 is a master regulator of B and T cell differentiation (both key immune system cells). Variants in this gene have been associated with multiple sclerosis, suggesting that it may influence immune tolerance and autoimmunity.

It is important to highlight that, although these genes are associated with an increased risk of developing multiple sclerosis, the presence of variants in these genes does not definitively determine the onset of the disease. Multiple sclerosis is a multifactorial condition in which genetic and environmental components interact.