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) :