A suspected case of IgG4-related bilateral arthritis of the knee

IgG4-related disease and other fibro-inflammatory conditions

IgG4-related disease (IgG4-RD) is a fibro-inflammatory disorder usually characterized by multi-organ involvement. Its pathogenesis is complex and involves genetic and environmental factors, while immune responses usually mediate organ damage and promote fibrosis, which is a key feature of the disease. IgG4 responses, however, are not exclusive to IgG4-RD and can be encountered in other diseases with phenotypes that partially overlap that of IgG4-RD. Although IgG4-RD has clinical and histological hallmarks, the lack of validated diagnostic criteria often makes the diagnosis challenging, requiring a multi-dimensional approach that integrates clinical, radiological and serological data. The present Review covers recent advances in the understanding of disease drivers and its clinical phenotypes, mainly focusing on the differential diagnosis with potential IgG4-RD mimickers, namely histiocytoses, lymphoproliferative disorders, systemic vasculitides and other immune-mediated conditions. The Review also provides a schematic approach to IgG4-RD treatment, including a brief overview of glucocorticoid-sparing agents and emerging therapies, from B cell-depleting monoclonal antibodies to cytokine-targeting drugs, the majority of which are currently under investigation in randomized clinical trials.

Thoracic paravertebral involvement in patients with IgG4-related disease: CT and MR imaging findings

OBJECTIVES

To retrospectively evaluate CT and magnetic resonance (MR) imaging thoracic paravertebral findings at baseline and follow-up in patients with IgG4-related disease.

METHODS

The study consisted of 36 patients with IgG4-related disease involving thoracic paravertebral regions (32 men and four women; mean age, 58 years; range, 25-78 years). A total of 36 patients underwent CT or MR imaging at baseline; 20 patients underwent follow-up. CT and MR images were reviewed and analysed in consensus by two radiologists for the various features of thoracic paravertebral lesions.

RESULTS

All lesions were located around two or more thoracic vertebrae, particularly the lower thoracic vertebrae (n = 36). The right side of vertebrae was predominantly affected in all cases (n = 36). Radiologically, IgG4-related thoracic paravertebral lesions were categorized into three types: solitary or multiple saddle-like masses type (32 patients); multiple nodules type (three patients); and invasively irregular mass type (three patients). All the types showed soft-tissue density on CT images, isointense on T1- and T2-weighted images, and homogeneous enhancement with penetration of small arteries in the lesions on contrast-enhanced CT and MR images. Steroid therapy administered to 20 patients dramatically diminished the mean maximum thickness in 18 patients. One patient with T7-12 vertebrae involved improved after steroid therapy.

CONCLUSION

IgG4-related paravertebral lesions occur mainly around the right side of the lower thoracic vertebrae and manifest as three major patterns of CT and MR imaging findings. Recognition of these diagnostic features will assist in the diagnosis and treatment of IgG4-related disease.

Immunoglobulin G4-Related Disease of the Hip

The authors report a case of immunoglobulin G4-related disease (IgG4-RD) of the hip. A 60-year-old man diagnosed with osteoarthritis of the right hip was referred to the authors' outpatient clinic for surgical intervention. Laboratory test results revealed elevated C-reactive protein and serum IgG levels. A subsequent laboratory test revealed an IgG4 level of 318 mg/dL. Magnetic resonance imaging revealed an abnormal mass in the right hip joint. The authors suspected IgG4-RD of the hip. The mass was resected during total hip arthroplasty. Immunohistochemical analysis for IgG revealed positive staining of many plasma cells. Most of the IgG-positive plasma cells were positive for IgG4, and the ratio of IgG4/IgG-positive cells was 51%. This case met all criteria for IgG4-RD; thus, the authors made a definitive diagnosis of IgG4-RD of the hip. The C-reactive protein level decreased to a negative value, and the IgG level decreased to a normal range at 3 weeks postoperatively. The IgG4 level gradually decreased to 152 mg/dL at 5 months postoperatively. This is the first reported case of IgG4-RD of the hip joint. [Orthopedics. 2018; 41(6):e876-e879.].