IgG4 related disease a nomenclature given in 2012 has wide clinical presentation involving mainly four subset (1) Pancreato-hepato-biliary disease (2) Retroperitoneal fibrosis and/or aortitis (3) Head and neck limited disease and (4) Classic Mikulicz syndrome with systemic involvement. Any clinical presentation has been strongly associated with infiltration of IgG4 plasma cells yet the pathogenesis of such infiltration is unknown. IgG4 related disease has manifestation as lymphadenopathy, autoimmune disease involving glands (endocrine and exocrine), pseudo tumor formation and eosinophilic fibrotic infiltrations over arteries, serosa, interstitial part of lung, respiratory mucosa, respiratory cartilages, skins and perineural spaces.
The course of illness is subacute to chronic however it is unlikely to have fever. Patient of IgG4 related disease are likely to have normal range blood cell count with/without eosinophilia, normal level inflammatory markers and complement factors. The close differentials are indolent infectious diseases like; HIV, tuberculosis, schistosomiasis, filariasis or various autoimmune diseases like; Sjogrens syndrome, Sarcoidosis, cryoglobulenemia, vasculitis or autoimmune deficiency like IgA, IgG deficiency or lymphoid and plasma cell related malignancies. IgG4 level or ratio of IgG4 to IgG level of the involved tissue has highly specific. However the cut off level of IgG4 can vary from one tissue to the other. Dense lymphoplasmacytic and eosinophilic infiltrate, storiform fibrosis, and obliterative phlebitis are highly specific microscopic finding. However storiform fibrosis and obliterative phelebitis are not seen with the disease of lymph node and bone marrow.
The diagnosis is based upon clinical manifestations with evidence of high level of IgG4 or classical histopathology. The disease response very well with steroid therapy however refractory cases have to be treated with azathioprine or mycophenolate or cyclophosphamide or rituximab. The duration of treatment is yet under-defined. Being a new entity and bizarre clinical manifestation this disease is expected to be under reported in clinical practices.
Key words: IgG4 related disease, Obliterative phelebitis, Steroids, Storiform fibrosis.