IgG4 Related Disease as a Differential Diagnosis in Multi-Organ Systemic Disease

IgG4 related disease is a relatively recently recognized systemic entity, that has been observed in nearly every organ system, with similar histopathological features across all identified organs. IgG4 is an antibody molecule accounting for less than 5% of the total IgG count in a healthy person. The molecule is implicated in numerous autoimmune diseases;however its role in IgG4 related disease, whether primary or secondary, remains unknown. The gold standard in the diagnosis of this condition is demonstration of organ involvement from biopsy specimens. In this case report, the patient had exhibited symptoms related mainly to the gastrointestinal tract for 12 years prior to his diagnosis of IgG4 related disease. After this patient’s diagnosis of IgG4 related disease, he was commenced on Rituximab, a monoclonal antibody, which was successful in subsiding his symptoms and he has remained symptom free for the past two years of follow up since commencing treatment and hadn’t developed any complications of the disease nor any complications related to treatment. IgG4 related disease is a systemic autoimmune disease that involves multiple organs 60% - 90% of the time, therefore clinicians should be aware that IgG4 related disease can mimic some autoimmune rheumatic diseases and place it as a differential diagnosis when multi-organ disease with systemic features is involved.