Background : Gallbladder cancer (GBC) is endemic in the northern part of India and hence any mass arising from gallbladder is cautiously dealt with .GBC has very many mimickers like xanthogranulomatous cholecystitis, adenomyomatosis, and among the rare entity is immunoglobulin G4(IgG4).Immunoglobulin G4 related disease (IgG4RD) is a rare condition encompassing multiorgan Involvement. It characteristically has lymphoplasmacytic infiltration, storiform fibrosis, and obliterative phlebitis on histology . A distinctive feature of this condition is the organ involvement with IgG4 positive plasma cells . Multiple organs can be involved either synchronously or metachronously; commonly affected organs are the pancreas, biliary tree, salivary glands, lacrimal glands, retroperitoneum, and lymph nodes .Isolated IgG4 disease is rare and can present as localized or diffuse type. The diffuse type is usually associated with IgG4 sclerosing cholangitis or pancreatitis while localized entity mimic malignancy.IgG4 related sclerosing cholecystitis is an uncommon entity, and isolated Involvement of the gallbladder without Involvement of the biliary tree and pancreas is infrequent. Furthermore, it has an atypical presentation, unlike the other types of cholecystitis . Therefore, only a few reports are available in the literature The epidemiology of this disease is poorly defined, and the concept is still in the fetal stage of evolution. It is attributable to the varied presentation, lack of well-defined criteria for diagnosis, or a single diagnostic modality . The majority of the data is from Japan and is insufficient to suggest increased predisposition in Asians . We herein report an outlying case of IgG4 related cholecystitis.

Methods : Not applicable since it was a case report.

Results : A focal gallbladder lesion is always malignant and benign aetiologies should be weighed in before undertaking a major surgery in an atypical presentation. Though a low threshold for a radical procedure is warranted to prevent missing timely treatment gallbladder cancer especially in endemic belt.

Conclusions : All gallbladder mass are not malignant and regional incidence can dictate the further course in case as ours.A low threshold for a radical approach warrants consideration after due deliberation.In-view of rarity of the disease , a high of suspicion should be exercised in an atypical presentation. A diagnosis of IgG4 cholecystitis pre-operatively can be a challenging.Careful consideration of diagnostic criteria and use of immunohistochemistry may aid in diagnosis as serum IgG4 sensitivity ranges between 50-60%.