Myeloperoxidase Antineutrophil Cytoplasmic Antibody (MPO-ANCA) Associated Crescentic and Necrotizing Glomerulonephritis (GN) with Membranoproliferative GN Features.

A 77-year-old man presented with a fever, non-productive cough, and edema formation. A laboratory analysis showed an elevated creatinine level (2.5 mg/dL), a high titer of myeloperoxidase (MPO)-anti-neutrophil cytoplasmic antibody (ANCA) (99 U/mL), positive reaction for antinuclear antibody (×320), hematuria, and massive proteinuria (3.33 g/day). A renal biopsy revealed crescentic and necrotizing glomerulonephritis (GN) with membranoproliferative GN features [double contour appearance of the glomerular basement membrane, granular deposition of immunoglobulin (Ig) G, IgM, and C3 along the capillary wall, subendothelial and subepithelial deposits with mesangial interposition]. A potential relationship between MPO-ANCA associated GN and membranoproliferative GN is discussed.

Expression of tight junction protein claudin-1 in human crescentic glomerulonephritis.

The origin of crescent forming cells in human glomerulonephritis (GN) remains unknown. Some animal studies demonstrated that parietal epithelial cells of Bowman's capsule (PECs) were the main component of proliferating cells and PEC-specific tight junction protein claudin-1 was expressed in crescentic lesions. We investigated the expression of claudin-1 in human GN. Immunohistochemistry for claudin-1 was performed on 17 kidney biopsy samples with crescent formation. Colocalization of claudin-1 with intracellular tight junction protein ZO-1 was also evaluated by immunofluorescence double staining. Claudin-1 is expressed mainly at the cell to cell contact site of proliferating cells in cellular crescentic lesions in patients with these forms of human GN. Small numbers of crescent forming cells showed extrajunctional localization of claudin-1. Colocalization of claudin-1 with ZO-1 was found at cell to cell contact sites of adjacent proliferating cells. In control samples, staining of claudin-1 was positive in PECs, but not in podocytes. Our findings suggest that claudin-1 contributes to crescent formation as a component of the tight junction protein complex that includes ZO-1. Co-localization of claudin-1 with ZO-1 implies the formation of functional tight junction complexes in crescentic lesions to prevent the interstitial damage caused by penetration of filtered molecules from Bowman's space.

A Case of Membranous Glomerulonephropathy Associated with Takayasu's Arteritis.

Glomerulonephropathy is a rare complication of Takayasu's arteritis (TA). To date, most glomerulonephropathies associated with TA show the histological feature of mesangial proliferation. Membranous glomerulonephropathy (MG) is a form of glomerulonephropathy in which the mesangial proliferation is not conspicuous and its association with TA is extremely rare. A 54-year-old man was referred to our hospital due to progressive edema in the lower limbs and nephrotic range proteinuria. Five years previously, he underwent percutaneous angioplasty for left subclavian artery stenosis. Kidney biopsy revealed stage II MG. General examination including enhanced CT scan confirmed the presence of TA. He started oral prednisolone therapy at a dose of 40 mg daily. The C-reactive protein level normalized 7 days after the prednisolone therapy. Three months later, proteinuria had remitted. Though the true relationship between MG and TA was not revealed in present case, considering the fact that complete remission of nephrotic syndrome occurred following the improvement of C-reactive protein level in response to steroid therapy, TA might be the secondary cause of MG. To our best knowledge, only two case reports described the association of MG and TA previously. Those two patients, however, also demonstrated the feature of systemic lupus erythematosus in addition to TA. This is the first case report that describes a patient who presented as MG associated with TA, but not complicated by systemic lupus erythematosus.

Persistent metabolic acidosis in a hemodialyzed patient with short bowel syndrome.

Short bowel syndrome (SBS) is characterized by a malabsorptive state. It is conceivable that the coexistence of SBS and end-stage renal disease can lead to severe metabolic acidosis; however, such a condition has rarely been documented. We herein describe the case of a 64-year-old man with SBS who required maintenance hemodialysis. Persistent metabolic acidosis and mineral and bone disorders should be of particular concern in hemodialyzed patients with SBS.