SNP Shot: Genomic Insights

Guillain-Barré syndrome (GBS) is an autoimmune condition where the body's immune system mistakenly attacks its own nerves. This happens when the immune system malfunctions and targets healthy tissues and organs. In GBS, this misdirected immune response specifically damages the peripheral nerves, which are responsible for connecting the brain and spinal cord (the central nervous system) to the rest of the body, including the limbs and organs. The immune attack often focuses on the axons, which are parts of the nerve cells (neurons) that transmit electrical signals. GBS can affect motor neurons (controlling movement), sensory neurons (transmitting sensations like pain, temperature, and touch), or both, leading to muscle weakness or sensory loss.

A hallmark of GBS is muscle weakness or paralysis, typically starting in the legs and progressing upwards to the arms, torso, and face. This is often accompanied by numbness, tingling, or pain. Other symptoms can include difficulty swallowing and breathing. In some cases, GBS affects the nerves that control involuntary bodily functions like blood pressure and heart rate, potentially resulting in fluctuating blood pressure or an irregular heartbeat (cardiac arrhythmia).

There are different types of GBS, classified according to the specific part of the peripheral nerve affected. The most common type is acute inflammatory demyelinating polyradiculoneuropathy (AIDP). In AIDP, the immune system damages myelin, a protective coating around nerve fibers (axons) that helps speed up nerve signal transmission. Two other types, acute motor axonal neuropathy (AMAN) and acute motor-sensory axonal neuropathy (AMSAN), involve direct damage to the axons themselves. AMAN affects only the axons of motor neurons, while AMSAN affects the axons of both motor and sensory neurons. Damage to sensory nerves can cause a loss of position sense and absent or diminished reflexes (areflexia).

Miller Fisher syndrome is another variant of GBS, affecting the cranial nerves, which extend from the brain to the head and neck. This syndrome is characterized by weakness or paralysis of the eye muscles (ophthalmoplegia), balance and coordination problems (ataxia), and areflexia. Individuals with Miller Fisher syndrome may also experience other common GBS symptoms, such as muscle weakness.

GBS can occur at any age, and it typically progresses through distinct phases. Most people with GBS experience a bacterial or viral infection before developing the condition. The initial phase, where symptoms worsen, can last up to four weeks, with the peak usually reached within one to two weeks. The second phase, the plateau, involves stabilization of symptoms and can last for weeks or months. Finally, the recovery phase involves improvement in symptoms. However, some individuals with GBS may not fully recover and may continue to experience fatigue, muscle weakness, or muscle pain.

Inheritance:

Almost all cases of GBS are sporadic, meaning they occur randomly in individuals without a family history of the condition. Although rare instances of multiple affected family members have been reported, GBS does not follow a clear inheritance pattern. The risk of developing GBS is likely influenced by a combination of genetic and environmental factors. Therefore, inheriting a gene associated with GBS does not guarantee that a person will develop the condition.