The pathophysiology of scleritis involves inflammation of scleral and episcleral tissue. The proposed mechanisms vary widely based on the subtype of scleritis and associated systemic causes including infectious, autoimmune, depositional, and drug induced. Idiopathic scleritis without any known systemic conditions can account for up to 50% of patients [1,2,3]. This case highlights the importance of including IgG4-related disease (IgG4-RD) in the differential for underlying causes of scleritis.
A widely accepted diagnostic criteria for IgG4-related ophthalmic disease (IgG4-ROD) described by Goto el al [8] incorporates a combination of enlargement of orbital tissues on imaging, marked plasmacytic infiltration on histopathology and elevated serum IgG4. Our patient meets the criteria for possible IgG4-related orbital disease, emphasizing the importance of evaluating other aspects of clinical history including history of episodes of pancreatitis, idiopathic retroperitoneal or aortic fibrosis, renal, parotid gland, and lacrimal gland involvement [9,10,11]. Isolated inflammation of sclera is an uncommon presentation of IgG4-ROD. Typically, lacrimal gland, followed by extraocular muscles and orbital fat are more commonly affected [10, 11]. Interestingly, prior individual case reports and case series have highlighted IgG4 disease as a cause of scleritis, however few have reported scleritis as an isolated ophthalmic manifestation of IgG4-ROD [9, 12,13,14].
While the exact inciting factor of IgG4-ROD is still unknown, proposed mechanisms have included a local inflammatory cascade triggered by infectious pathogen, autoantigens, or genetic predisposition [10, 11]. Regardless of the spectrum of disease, the involved tissues show a lymphoplasmacytic infiltration leading to obliterative phlebitis and fibrosis if left untreated or undertreated [8, 10, 15]. The current case demonstrated a partial response to initial topical corticosteroid and systemic immunomodulatory therapy, highlighting the need for tailoring therapy to individual response as well as high likelihood of disease relapse [3, 9, 10].