Keshan disease (KD)

Keshan Disease (KD): Causes, Symptoms, and Prevention

Keshan disease (KD) is a rare but serious condition that primarily affects the heart. It is named after the Keshan County in China, where the disease was first discovered in the 1930s. KD is characterized by cardiomyopathy (damage to the heart muscle), which can lead to heart failure and other life-threatening complications. The disease is most commonly associated with a selenium deficiency, an essential trace mineral that plays a crucial role in many biological processes, including protecting cells from oxidative stress.

What Causes Keshan Disease?

The main cause of Keshan disease is a deficiency in selenium, a vital antioxidant that helps prevent cellular damage and supports proper heart function. Selenium is found naturally in soil and foods, but in certain regions, such as parts of China, the soil is extremely low in selenium, which affects the local food supply. People living in these areas are more likely to develop selenium deficiency, putting them at risk for Keshan disease.

In addition to selenium deficiency, it is believed that viral infections, specifically Coxsackievirus B, may act as a co-factor in the development of KD. This virus, when combined with low selenium levels, may further weaken the heart muscle and increase the risk of cardiomyopathy.

Symptoms of Keshan Disease

The symptoms of Keshan disease can vary depending on the severity and progression of the condition. The disease typically manifests as acute, subacute, or chronic cardiomyopathy.

1. Acute Keshan Disease: This form of the disease develops suddenly and is the most dangerous. Symptoms may include:

   • Severe chest pain
   • Shortness of breath
   • Sudden onset of heart failure
   • Shock
   • Arrhythmias (irregular heartbeats)

2. Subacute Keshan Disease: This form progresses more slowly and may show symptoms such as:

   • Fatigue
   • Swelling in the legs or abdomen (edema)
   • Persistent coughing, especially when lying down
   • Mild chest pain or discomfort
   • Symptoms of heart failure

3. Chronic Keshan Disease: In the chronic phase, symptoms develop gradually over time and can include:

   • Weakness
   • Decreased exercise tolerance
   • Symptoms of chronic heart failure
   • Persistent shortness of breath

How Does Selenium Deficiency Cause Keshan Disease?

Selenium is an important component of glutathione peroxidase, an enzyme that protects cells from oxidative stress and inflammation. When selenium levels are too low, the body's ability to neutralize free radicals and repair cellular damage is compromised, leading to an increased risk of damage to the heart muscle.

In regions with selenium-poor soil, dietary intake of this trace mineral is insufficient to meet the body’s needs. As a result, individuals living in these areas, particularly those with poor diets, are more susceptible to the damaging effects of oxidative stress, which can contribute to the development of KD.

Risk Factors for Keshan Disease

Keshan disease most commonly affects people living in selenium-deficient regions, especially in rural parts of China. However, other factors that increase the risk of developing KD include:

• Poor Diet: A diet lacking in selenium-rich foods, such as meat, fish, eggs, and certain nuts, increases the risk.
• Geographic Location: The disease is primarily found in areas where the soil is low in selenium, such as certain regions of China, parts of Russia, and New Zealand.
• Viral Infections: Exposure to Coxsackievirus B may increase the likelihood of developing KD, especially in selenium-deficient individuals.
• Genetic Susceptibility: Some studies suggest that individuals with certain genetic backgrounds may be more vulnerable to Keshan disease, although more research is needed to fully understand this relationship.

How is Keshan Disease Diagnosed?

Diagnosing Keshan disease involves a combination of clinical evaluation, patient history, and laboratory tests. Physicians will typically look for signs of cardiomyopathy and heart failure. Blood tests to measure selenium levels and glutathione peroxidase activity can help confirm a selenium deficiency. In addition, doctors may use electrocardiograms (ECGs), echocardiograms, and chest X-rays to assess the function of the heart and detect any abnormalities associated with cardiomyopathy.

Treatment and Prevention of Keshan Disease

1. Selenium Supplementation: The primary treatment for Keshan disease is to restore selenium levels in the body. This is done through selenium supplementation, which can reverse the symptoms of the disease in its early stages and prevent further heart damage. Foods rich in selenium include:

   • Brazil nuts
   • Fish (e.g., tuna, sardines)
   • Eggs
   • Poultry
   • Whole grains
   • Seeds

   Selenium supplements are also available in tablet or capsule form, and they are commonly used to treat those in high-risk areas.

2. Supportive Care for Heart Function: In cases where heart failure has developed, patients may need additional treatment to manage heart function. This can include medications like:

   • Diuretics to reduce fluid buildup
   • ACE inhibitors or beta-blockers to improve heart function
   • Antivirals if Coxsackievirus B infection is confirmed

   In severe cases, hospitalization and more intensive interventions may be necessary.

3. Preventive Measures: Prevention of Keshan disease focuses on ensuring adequate selenium intake, especially for populations living in selenium-deficient regions. Public health initiatives in China and other affected areas have successfully reduced the incidence of Keshan disease by fortifying food with selenium and educating the population about the importance of selenium-rich diets.

Long-Term Outlook for Keshan Disease

The prognosis for individuals with Keshan disease depends on the stage at which the disease is detected and treated. In the early stages, selenium supplementation can significantly improve symptoms and prevent permanent heart damage. However, if the disease progresses to severe cardiomyopathy or heart failure, the damage to the heart may be irreversible, leading to a poorer outcome.

Prompt diagnosis and treatment are crucial in preventing long-term complications. With proper selenium intake and early medical intervention, many individuals can recover from the disease or prevent its onset entirely.

Conclusion

Keshan disease is a preventable condition primarily caused by selenium deficiency, which affects the heart and can lead to serious health consequences. While the disease was historically prevalent in certain selenium-deficient regions of China, increased awareness and public health efforts have greatly reduced its incidence.

To prevent Keshan disease, individuals living in selenium-poor areas should ensure they are consuming adequate amounts of selenium through diet or supplementation. In cases where selenium deficiency is detected, early intervention with supplements can prevent the progression of the disease and protect heart health. As more research continues to uncover the interactions between selenium, viral infections, and genetic factors, our understanding of how to prevent and treat Keshan disease will continue to improve.