Eosinophilic diseases
Eosinophils are white blood cells that play an important role in the body's response to allergic reactions, asthma, and parasite infection. These cells participate in protective immunity against certain parasites, but they also contribute to the inflammation in allergic disorders.
Sometimes eosinophils cause inflammation in certain organs, which results in symptoms.
Generally, eosinophils constitute less than 7% of circulating white blood cells (100 to 500 eosinophils per microliter of blood [0.1 to 0.5 × 10 9 per liter]).
The low number of eosinophils
A reduced number of eosinophils in the blood (eosinopenia) can occur in Cushing's syndrome, bloodstream infections ( sepsis ), and corticosteroid treatment. However, fewer eosinophils usually do not cause problems, as other parts of the immune system adequately compensate.
A reduced number of eosinophils is usually detected by chance when a complete blood count is performed for other reasons.
Treating the cause restores the normal number of eosinophils.
The high number of eosinophils
The most common causes of a high number of eosinophils (called eosinophilia or hypereosinophilia) are:
- Allergic Disorders
- parasite infections
- Certain types of cancer
Many parasites, especially those that invade tissues, cause eosinophilia. Allergic disorders, including drug sensitivities, asthma, allergic rhinitis, and atopic dermatitis, often increase eosinophils. Cancers that cause eosinophilia include Hodgkin's lymphoma, leukemia, and certain myeloproliferative neoplasms .
If the number of eosinophils is only slightly elevated, people generally have no symptoms, and the high number of eosinophils in the blood is only discovered when an FBC is taken for other reasons. However, sometimes, especially when eosinophils are very high, the increase causes tissue inflammation and organ damage. The organs most frequently affected are the heart, lungs, skin, and nervous system, but any organ can be damaged.
Symptoms are related to the affected organ. For example, people may experience a rash when the skin is affected, wheezing and shortness of breath when the lungs are affected, shortness of breath and fatigue (symptoms of heart failure ) when the heart is affected, or sore throat and stomach, When the esophagus or stomach is affected. Consequently, eosinophilic diseases are diagnosed according to where eosinophil levels are elevated:
- Eosinophilic pneumonia (lungs)
- Eosinophilic cardiomyopathy (heart)
- Eosinophilic esophagitis (esophagus)
- Eosinophilic gastritis (stomach)
- Eosinophilic enteritis (small intestine)
- Eosinophilic colitis (large intestine)
Often, people first get tested and are treated for the most common causes of their symptoms. For example, they can be screened for infection and even given antibiotics even if no infection is found. Because people continue to have symptoms after treatment, doctors often take a tissue sample for examination (a biopsy) to show eosinophils within the affected organ.
Treatment of these conditions often includes oral corticosteroids.
Hypereosinophilic syndrome
Hypereosinophilic syndrome is an uncommon disorder in which the number of eosinophils increases to more than 1500 cells per microliter of blood (more than 1.5 × 10 9 per liter) for more than six months with no obvious cause. Some people have a rare chromosomal disorder.
People of any age can develop the hypereosinophilic syndrome, but it is more common in men over 50 years of age. Many eosinophils can damage the heart, lungs, liver, skin, and nervous system. The heart, for example, can become inflamed in a clinical condition called Löffler's endocarditis, which leads to the formation of blood clots, heart failure, myocardial infarctions, or malfunctioning heart valves .
Symptoms may include weight loss, fevers, night sweats, fatigue, cough, chest pain, bloating, stomach pain, rash, pain weakness, confusion, and coma. Some additional symptoms of this syndrome depend on which organs are damaged.
This syndrome is suspected when repeated blood tests reveal that eosinophils are persistently elevated in people with these symptoms. The diagnosis is confirmed when doctors determine that eosinophilia is not caused by a parasitic infection, allergic reaction, or other diagnosable disorder and when biopsies show eosinophils within organs.
Without treatment, usually, more than 80% of people who suffer from this syndrome die in less than two years; with treatment, more than 80% survive. Some people do not need any treatment other than careful observation for three to six months, but most need drug treatment with prednisone, hydroxyurea, or chemotherapy drugs.
Some people with the hypereosinophilic syndrome have an acquired abnormality in a gene that regulates cell growth. This type of hypereosinophilia may respond to treatment with imatinib, a drug used to treat cancer. If treatment with these drugs is unsuccessful, several other drugs can be used, and these can be combined with a procedure to eliminate eosinophils from the blood ( leukapheresis ).
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