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IgG4-associated sclerosing disease

Sunday 22 November 2009

IgG4-related sclerosing disease encompasses a spectrum of fibroinflammatory lesions that affect various organ systems including the pancreas, bile duct, gallbladder, retroperitoneum, salivary gland, aorta, lacrimal gland, kidney, mediastinum, and lung.

Manifestations in these organs consist of tumorlike masses and/or fibrosis associated with infiltration by numerous IgG4-positive plasma cells and lymphocytes. Affected patients often have high levels of serum IgG4.

Histologic features were initially described in cases of autoimmune pancreatitis and include :
- (1) dense fibrosis with an associated mixed inflammatory infiltrate with IgG4-positive plasma cells,
- (2) infiltration or granulomas in some cases,
- (3) obliterative phlebitis.

Subsequent reports have shown similar features at sites of extrapancreatic involvement. Diagnosis of IgG4-related sclerosing disease is important to avoid unnecessary surgery from a misdiagnosis of malignancy. In addition, the lesions often respond readily to steroid therapy.

While IgG4-related sclerosing disease was initially reported in the context of autoimmune pancreatitis, recent reports have shown that pulmonary involvement may occur in association with, or sometimes independently from, autoimmune pancreatitis.

Reported pulmonary manifestations of IgG4-related sclerosing disease have included:
- fibroinflammatory masses,
- the plasma cell–rich variant of inflammatory pseudotumor,
- interstitial pneumonitis resembling idiopathic nonspecific interstitial pneumonia (NSIP),
- some lesions formerly thought to represent grade I lymphomatoid granulomatosis.

Some cases of sclerosing mediastinitis, which may secondarily affect the lung, have also been reported as a manifestation of IgG4 systemic sclerosing disease.

The overlap in clinical, morphologic, and immunohistochemical features between these entities suggest that they represent different morphologic manifestations of the same clinicopathologic entity.

References

- Update on nonneoplastic pulmonary lymphoproliferative disorders and related entities. Guinee DG Jr. Arch Pathol Lab Med. 2010 May;134(5):691-701. PMID: 20441500

- IgG4-related Sclerosing disease: a potential new etiology of cutaneous pseudolymphoma. Cheuk W, Lee KC, Chong LY, Yuen ST, Chan JK. Am J Surg Pathol. 2009 Nov;33(11):1713-9. PMID: 19701072

- Inflammatory myofibroblastic tumor versus IgG4-related sclerosing disease and inflammatory pseudotumor: a comparative clinicopathologic study. Yamamoto H, Yamaguchi H, Aishima S, Oda Y, Kohashi K, Oshiro Y, Tsuneyoshi M. Am J Surg Pathol. 2009 Sep;33(9):1330-40. PMID: 19718789