Systemic Exertional Intolerance Disease (SEID)

Systemic Exertional Intolerance Disease (SEID) is a chronic, complex medical condition characterized by profound fatigue and other symptoms that worsen after physical or mental exertion. The term SEID was introduced in 2015 by the Institute of Medicine (now known as the National Academy of Medicine) to replace the previously used terms Chronic Fatigue Syndrome (CFS) and Myalgic Encephalomyelitis (ME).

Definition and Diagnostic Criteria

The diagnostic criteria for SEID include:

• A substantial reduction or impairment in the ability to engage in pre-illness levels of occupational, educational, social, or personal activities that persists for more than 6 months and is accompanied by fatigue.
• The worsening of symptoms after physical or mental exertion (post-exertional malaise).
• Unrefreshing sleep.
• Cognitive impairment, such as difficulty with concentration or memory.
• Orthostatic intolerance, which is the inability to tolerate an upright posture due to symptoms that worsen when standing and improve when lying down.

Symptoms

The symptoms of SEID can vary in severity and may include:

• Prolonged and profound fatigue that is not relieved by rest.
• Post-exertional malaise, which is a worsening of symptoms after physical or mental activity.
• Muscle pain (myalgia) and joint pain (arthralgia).
• Headaches.
• Sensitivity to light and sound.
• Irritability, anxiety, and depression.
• Gastrointestinal symptoms, such as irritable bowel syndrome.

Cause and Pathophysiology

The exact cause of SEID is not well understood. However, research suggests that it may involve a combination of genetic, environmental, and infectious factors. Some potential triggers include:

• Infections, such as viral or bacterial infections.
• Autoimmune disorders, in which the immune system mistakenly attacks healthy tissues.
• Hormonal imbalances.
• Neurological factors, such as abnormalities in brain function and structure.

Treatment and Management

Treatment for SEID typically focuses on managing symptoms and improving quality of life. This may include:

• Pacing activities to avoid exacerbating symptoms.
• Getting regular, gentle exercise, such as yoga or stretching.
• Practicing stress-reducing techniques, such as meditation or deep breathing.
• Improving sleep habits.
• Taking medications to manage pain, sleep disturbances, and other symptoms.

Prognosis and Outlook

The prognosis for SEID varies widely depending on the individual and the severity of their symptoms. Some people may experience significant improvement with treatment, while others may continue to experience debilitating symptoms. Research is ongoing to better understand SEID and develop more effective treatments.