DISCUSSION:
The most prevalent reasons for increased eosinophil count are parasitic infections, allergy/atopy, urticaria, eczema, allergic rhinitis, angioneurotic oedema, reactive eosinophilia subsequent to T-cell lymphoma, acute leukaemia, B-cell lymphoma, eosinophilic leukaemia, allergic drug reactions, idiopathic hyper-eosinophilic syndrome, and collagen vascular diseases such as rheumatoid arthritis, eosinophilic fasciitis, or allergic angiitis [9].
Although TB is not a well-known cause of eosinophilia in the medical literature, it was identified in our case. Based on current evidence, there have been few reported instances of this phenomenon in recent years. Flores et al. described a similar case of peripheral blood eosinophilia and TB, which included symptoms such as lethargy, weight loss, and lymphadenopathy and was confirmed by a lymph node biopsy that revealed a granulomatous lesion [10]. Gill et al. reported a case of abdominal tuberculosis with peripheral eosinophilia. The patient was diagnosed with abdominal tuberculosis based on a histopathological examination of peritoneal tissue [8]. Similarly, Garg et al. reported a case of peripheral blood eosinophilia and TB, which included symptoms such as cough, generalized weakness, and significant weight loss and was confirmed by endoscopic bronchial ultrasound-guided fine-needle aspiration of the mediastinal lymph node that revealed acid-fast bacilli [5].
Ray et al. proposed that after experiencing an early hypersensitive reaction to the Mycobacterium antigen, susceptible people can develop florid tropical pulmonary eosinophilia [11]. IL-5 has been shown to be the main cytokine driving the development of peripheral eosinophilia in people with pulmonary TB. The release of toxic eosinophil products is closely associated with tissue pathology. Examples of such by-products are eosinophil cationic protein, major basic protein, and eosinophil-derived neurotoxin. Potentially, the emission of reactive oxygen species may cause tissue injury [12]. The normal range of eosinophils in blood is between 0.0 and 6.0 %, and between 30 and 350 is the typical range for the AEC. AEC between 0.5 and 1.0 x109/L (SI units) or 0.5 and 1.0 x103 cells/microliter (conventional units) is considered to be mild blood eosinophilia, whereas AEC greater than or equal to 1.5 x109/L is considered to be hyper-eosinophilia [13]. Our patient presented with an AEC of 70%, accounting for 25,920 cells, and a TLC of 36,000.
Hsu et al. reported that patients undergoing peritoneal dialysis had modest peripheral blood and peritoneal fluid eosinophilia. The eosinophilia persisted despite the cessation of dialysis, but it disappeared following the initiation of anti-tuberculous treatment [14]. Similarly, Haftu et al. reported a rare case of hepatic TB with significant peripheral eosinophilia [15]. Our patient’s imaging results aided in clinching the diagnosis. Further evidence supporting the link between TB and peripheral eosinophilia is the patient’s positive clinical response to anti-TB therapy with Ethambutol, Rifampicin, Isoniazid, and Pyrazinamide for the initial two months, followed by Rifampicin and Isoniazid for the next four months (2ERHZ/4RH). Patients with peripheral eosinophilia should have TB considered as a differential diagnosis, particularly after more prevalent reasons have been ruled out.
A few similar cases in the literature are described below (Table 2) :