Eosinophilia refers to an increase in peripheral blood eosinophils above the normal range (>5% or an absolute count >0.5×10⁹/L).

bubble_chart Etiology

Disease causes are varied:

1. Chinese Taxillus Herb infestation: Most common, various Chinese Taxillus Herb larvae migrating into organs or adult worms damaging the intestinal mucosa can cause this disease. Tropical eosinophilia and Loffler's syndrome are closely related to migrating larval infections.
2. Allergic diseases: Urticaria, bronchial asthma, serum sickness, drug allergies, etc.
3. Certain medications: Penicillin, cephalosporins; phenytoin sodium, sulfonamides, chlorpromazine, etc.
4. Infections: Certain bacterial, viral, spirochetal infections, and insect bites that produce allergic reactions.
5. Associated with other diseases: Certain connective tissue diseases (nodular polyarteritis, Bi disease), ulcerative colitis, chronic kidney diseases, certain tumors, etc.

bubble_chart Diagnosis

(1) A peripheral blood eosinophil count >0.5×10⁹/L can be diagnosed. There is still a lack of unified criteria for clinical grading.

1. Grade I: Eosinophils > normal, <15%，直接計數<1.5×10⁹/L.
2. Grade II: Eosinophils increase to 15–49%, with a direct count of 1.5×10⁹/L to 5.0×10⁹/L.
3. Grade III: Eosinophils increase to 50–90%, with a direct count >5×10⁹/L.

1. Tropical eosinophilia:
   1. Onset is slow, course is long, with recurrent fever, lack of strength, anorexia, and weight loss, possibly accompanied by urticaria.
   2. Recurrent cough and panting, with few lung signs, though wheezing and rales may sometimes be heard. Chest X-ray shows increased markings, possibly with patchy shadows or hilar lymphadenopathy.
   3. Hepatosplenomegaly and lymphadenopathy may occur.
   4. Leukocytosis is present, with significant eosinophilia, often >20%, and direct counts typically show moderate to Grade III increases. Bone marrow examination reveals eosinophilia, predominantly in the middle and late stages, with no other abnormalities.
   5. Eosinophils are increased in sputum, and Chinese Taxillus Herb eggs may be found in stool.
   6. Cold agglutination test may show a positive reaction.
   7. Treatment with carbarsone or hetrazan yields good results.
2. Allergic pneumonia is a pulmonary hypersensitivity reaction caused by larval migration or other antigens. Symptoms may include low-grade fever, mild cough, lack of strength, or no symptoms; eosinophils are increased in sputum; chest X-ray shows low-density migratory patchy shadows, which often resolve spontaneously within days to half a month without special treatment; blood eosinophils are mostly Grade II increased and usually return to normal within weeks; prednisone and anthelmintic treatment are highly effective.
3. Epidemic explosive eosinophilia, also known as pestilential eosinophilia, may be related to acute massive Ascaris infection or allergic reactions caused by viruses or fungi. Characteristics include acute onset, epidemic nature, and short course; fever and chest pain are prominent, with spasmodic cough and wheezing worsening at night; hetrazan and prednisone are effective for cases caused by Ascaris larvae.
4. Eosinophilic lymphogranuloma: The cause of the disease is unknown but may be related to allergic reactions, with a higher incidence in males. Clinically, granulomas commonly occur in lymph nodes or (and) soft tissues of the jaw, face, neck, and upper arms, with a rubbery texture; the skin of the tail may be dry and coarse with pigmentation and cutaneous pruritus; the masses grow slowly and may be accompanied by fever and lack of strength; leukocytosis and eosinophilia are present, and bone marrow shows significant eosinophilia; pathological examination of granulomas reveals intense lymphoid tissue and eosinophil infiltration, with proliferative lymphoid follicles; the condition is sensitive to radiation and hormonal therapy, but recurrence is common with hormonal treatment alone.
5. Eosinophilic asthma: This is an allergic disease caused by Ascaris infection, with a course lasting several years. Characteristics include wheezing, worsening at night, paroxysmal choking cough, and wheezing in both lungs; may be accompanied by urticaria; blood eosinophils are increased, and nasal and pharyngeal secretions contain large numbers of eosinophils; anthelmintic and anti-allergy treatments show significant efficacy.

bubble_chart Treatment Measures

(1) Disease Cause Treatment

Deworming, treatment of infectious and allergic diseases, etc.

(2) For mild cases with generally unknown causes and lack of clinical manifestations, no special treatment is required, and follow-up may be provided. When there is persistent grade III elevation, the following medications may be selected for treatment.

1. Carbamazepine 8mg/(kg·d), divided into 2-3 oral doses per day, with a 10-day course of treatment. If necessary, another course may be taken after 10 days. It is suitable for treating tropical eosinophilia and is contraindicated in patients with liver or kidney dysfunction.
2. Diethylcarbamazine 4-6mg/(kg·d), divided into 2-3 oral doses per day, taken continuously for 7-14 days, or 12-15mg/(kg·d), divided into 3 oral doses per day, taken continuously for 4-5 days. It is suitable for treating filariasis, tropical eosinophilia, epidemic eosinophilia, and eosinophilia of unknown cause.
3. Prednisone can be used for severe allergic pneumonia, epidemic eosinophilia, etc., at 1-1.5mg/(kg·d), taken orally for about 2 weeks. The dosage should be gradually reduced after the condition improves and maintained for 4-6 weeks. For recurrent cases, the treatment course may be extended.