IgG4-related disease is a recently recognized multi-organ disorder characterized by high levels of serum IgG4 and dense infiltration of IgG4-positive cells into several organs. Although the pancreas was the first organ recognized to be affected by IgG4-related disorder in the syndrome of autoimmune pancreatitis, we present here clinico-pathological features of 23 patients diagnosed as having renal parenchymal lesions. These injuries were associated with a high level of serum IgG4 and abundant IgG4-positive plasma cell infiltration into the renal interstitium with fibrosis. In all patients, tubulointerstitial nephritis was the major finding. Although 14 of the 23 patients did not have any pancreatic lesions, their clinicopathological features were quite uniform and similar to those shown in autoimmune pancreatitis. These included predominance in middle-aged to elderly men, frequent association with IgG4-related conditions in other organs, high levels of serum IgG and IgG4, a high frequency of hypocomplementemia, a high serum IgE level, a patchy and diffuse lesion distribution, a swirling fibrosis in the renal pathology, and a good response to corticosteroids. Thus, we suggest that renal parenchymal lesions actually develop in association with IgG4-related disease, for which we propose the term 'IgG4-related tubulointerstitial nephritis.'

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IgG4-related disease is a new disease classification established in Japan in the 21st century. Patients with IgG4-related disease display hyper-IgG4-gammaglobulinemia, massive infiltration of IgG4+ plasma cells into tissue, and good response to glucocorticoids. Since IgG4 overexpression is also observed in other disorders, it is necessary to diagnose IgG4-related disease carefully and correctly. We therefore sought to determine cutoff values for serum IgG4 and IgG4/IgG and for IgG4+/IgG+ plasma cells in tissue diagnostic of IgG4-related disease. Patients and Methods. We retrospectively analyzed serum IgG4 concentrations and IgG4/IgG ratio and IgG4+/IgG+ plasma cell ratio in tissues of 132 patients with IgG4-related disease and 48 patients with other disorders. Result. Serum IgG4 >135  mg/dl demonstrated a sensitivity of 97.0% and a specificity of 79.6% in diagnosing IgG4-related disease, and serum IgG4/IgG ratios >8% had a sensitivity and specificity of 95.5% and 87.5%, respectively. IgG4+cell/IgG+ cell ratio in tissues >40% had a sensitivity and specificity of 94.4% and 85.7%, respectively. However, the number of IgG4+ cells was reduced in severely fibrotic parts of tissues. Conclusion. Although a recent unanimous consensus of all relevant researchers in Japan recently established the diagnostic criteria for IgG4-related disease, findings such as ours indicate that further discussion is needed.

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Abstract-An attractive formulation of the sampling problem is based on the principle of a consistent signal reconstruction. The requirement is that the reconstructed signal is indistinguishable from the input in the sense that it yields the exact same measurements. Such a system can be interpreted as an oblique projection onto a given reconstruction space. The standard formulation requires a one-to-one relationship between the input measurements and the reconstructed model. Unfortunately, this condition fails when the cross-correlation matrix between the analysis and reconstruction basis functions is not invertible; in particular, when there are less measurements than the number of reconstruction functions. In this paper, we propose an extension of consistent sampling that is applicable to those singular cases as well, and that yields a unique and well-defined solution. This solution also makes use of projection operators and has a geometric interpretation. The key idea is to exclude the null space of the sampling operator from the reconstruction space and to enforce consistency on its complement. We specify a class of consistent reconstruction algorithms corresponding to different choices of complementary reconstruction spaces. The formulation includes the Moore-Penrose generalized inverse, as well as other potentially more interesting reconstructions that preserve certain preferential signals. In particular, we display solutions that preserve polynomials or sinusoids, and therefore perform well in practical applications.