In most cases of acute cholecystitis, gallstone impaction starts the inflammatory process. The bile accumulates in the gall bladder and causes chemical irritation, and may facilitate bacterial invasion [7,11].

Few case reports and case series are available in the literature about EC. The prevalence of EC ranges from 0.25 to 6.4%, as reported in multiple studies [1,3,4]. Although few case reports are describing EC, the etiopathogenesis is still not well known [5]. In a series by Fox et al. (12,13),  625 gallbladders were evaluated, in which 16 of them exhibited eosinophilic infiltration. In the series published by Dabbs et al. [5], 217 gallbladders were assessed over two years, and in 14 (6.5%) of the EC were observed. A study reported by Muhlberger et al. [14] 55 of 660 resected gallbladders (8.3%) had ≥25% eosinophilic infiltration.

A search in the literature revealed 27 individuals with acute cholecystitis accounts of EC since 1949. The majority of them have associated with HES and eosinophilic cholangiopathy, parasitic infestation, or acalculous cholecystitis [3,4,8,10,11]. When peripheral eosinophilia is observed, the diagnosis of HES should be considered [2].

Acalculous cholecystitis is another cause of eosinophilic cholecystitis, with the invasion of the mucosal surface by eosinophils [15]. Causes of acute acalculous cholecystitis are different, including critical illness, major burns,  herbal medicine [16,17]. Patients with acalculous cholecystitis are three to four times more likely to have EC than patients with gall stone.

If no etiology was found, the case is considered one of idiopathic EC. Idiopathic cholecystitis is crucial because laboratory tests can not diagnose it. By considering peripheral eosinophilia, one must think of the number of etiologies that may cause such disease.

Abdominal Ultrasound results may be unremarkable or show signs suggestive of typical cholecystitis such as gallbladder distension, wall thickening, or sonographic Murphy sign [10].

In our patient peripheral eosinophilia, about 7% was noted during the hospital course. The etiology for eosinophilia was unknown. Cholecystectomy led to full recovery, and the patient was discharged without any complications. Due to peripheral eosinophilia, we recommended evaluating the patient for the hyper-eosinophilic syndrome, eosinophilic gastroenteritis, and parasitosis.

Because EC can happen may occur in many conditions, and it can be associated with other diseases; therefore, when it is diagnosed, possible associated etiologies should be investigated. Pathologists should carefully differentiate EC from other causes of cholecystitis, which may have a worse prognosis than the cholecystitis itself [18-21].

EC prognosis is good [22]. When the disease is limited to the gall bladder, the treatment of choice is cholecystectomy, preferably performed laparoscopically [23,24].