Immunoglobulin G (IgG) nephropathy refers to a rare group of diseases characterized by deposits of IgG in the mesangial region. However, IgG nephropathy is controversial as a single disease entity, and its pathogenesis remains to be elucidated. In the present report, we discuss a case of IgG nephropathy in which we observed activation of the classical complement pathway.A 47-year-old woman was admitted to our hospital with nephrotic syndrome. Light-microscopic examination revealed neither proliferative nor sclerotic lesions in the glomeruli. However, unusual and large deposits were observed in the paramesangial area. An immunofluorescence study revealed predominant IgG and C1q and slight C3 deposits in the paramesangial area, suggesting immune-complex-type glomerular disease. An electron microscopic study also revealed different sizes of non-organized electron-dense deposits with a similar pattern of distribution, which were accompanied by foot process effacement. Clinically, there was no evidence of systemic diseases, such as infectious or autoimmune diseases (including systemic lupus erythematosus). Based on these findings, she was diagnosed with IgG nephropathy and treated with prednisolone. Steroid therapy was effective, and complete remission was maintained.Additional immunological examination revealed that IgG deposits were polyclonal and consisted mainly of the IgG1 and IgG3 subclasses. Furthermore, staining was positive for C4d and C5b-9. The present findings indicate that the pathogenesis of IgG nephropathy in our patient may have involved activation of the classical complement pathway.

As mRNA COVID-19 vaccines have become widely available, cases of new-onset glomerular disease after receiving COVID-19 vaccination have been reported. Here, we present a case of kidney biopsy-proven new-onset IgA vasculitis after receiving the mRNA-1273 (Moderna) COVID-19 vaccination. A 47-year-old man with a 10-year medical history of hypertension and hyperuricemia visited our hospital 19 days after receiving an initial mRNA-1273 COVID-19 vaccine injection for purpuric eruption on the legs and dorsal regions of the feet. Although the eruptions spontaneously improved within 5 days, they developed again at 15 days after the second injection. A histopathological examination of skin biopsy specimens was reminiscent of leukocytoclastic vasculitis, though direct immunofluorescence did not indicate IgA deposition within small vessel walls. Urinalysis indicated severe proteinuria (3 +) and occult blood (3 +). Thus, a kidney biopsy was performed and light microscopy revealed mild mesangial expansion, hypercellularity, and endocapillary hypercellularity, with cellular and fibrocellular crescents observed in three and one, respectively, of a total of 15 glomeruli. Immunofluorescence also showed diffuse granular mesangial staining (3 +) for IgA. Histopathological features were consistent with IgA vasculitis. Intravenous methylprednisolone at 1000 mg for 3 days was initiated, followed by oral prednisolone (0.6 mg/kg/day). Over the following 2-week period, serum creatinine level improved from 1.24 to 1.06 mg/dL and proteinuria decreased from 2.98 to 0.36 g/g Cr, though occult blood persisted. Findings in the present case indicate that new-onset IgA vasculitis after receiving mRNA-1273 COVID-19 vaccine can be treated with corticosteroid therapy.

Immunoglobulin M nephropathy (IgMN) is an idiopathic glomerulopathy characterized by diffuse global mesangial deposits of IgM. We retrospectively studied the clinical and histopathological characteristics of the patients with IgMN seen in our service. Of 241 renal biopsies, 21 corresponded to IgMN (8.7 %). One patient was excluded due to associated systemic disease and 2 due to follow-up less than 1 year, 18 were included (14 girls, median age 3.08 years). Fourteen manifested with nephrotic syndrome (NS) and the remaining with proteinuria (isolated or associated with hematuria). On Nefropatía por inmunoglobulina M: características histopatológicas y clínicas. Serie de casos Immunoglobulin M nephropathy: histopathological and clinical characteristics. Case series light microscopy, 13 had hyperplasia with mesangial expansion and 5 had focal and segmental sclerosis. Of the patients with NS, 7 were steroid-resistant, 4 steroid-dependent, and 3 frequent relapsers. All patients with NS and 1 with proteinuria-hematuria received immunosuppressants; the 18 patients also received antiproteinuric drugs. After 5.2 years (2-17.5) of follow-up, 6 patients developed chronic kidney disease.
La nefropatía por inmunoglobulina M (NIgM) es una glomerulopatía idiopática caracterizada por depósitos mesangiales globales y difusos de IgM. Se realizó un estudio retrospectivo de las características clínicas e histopatológicas de los pacientes con NIgM atendidos en nuestro servicio. De 241 biopsias renales, 21 correspondieron a NIgM (8,7 %). Se incluyeron 18 pacientes (14 de sexo femenino, mediana de edad: 3,08 años). Se excluyó a 1 paciente por enfermedad sistémica asociada y a 2 por seguimiento menor a 1 año. Catorce pacientes se manifestaron con síndrome nefrótico (SN) y 4 con proteinuria aislada o asociada a hematuria. En la microscopia óptica, 13 presentaron hiperplasia mesangial, y 5 esclerosis focal y segmentaria. De los pacientes con SN, 7 fueron corticorresistentes, 4 corticodependientes y 3 presentaban recaídas frecuentes. Todos los pacientes con SN y 1 con proteinuria-hematuria recibieron inmunosupresores; los 18 pacientes recibieron, además, antiproteinúricos. Luego de 5,2 años (2-17,5) de seguimiento, 6 pacientes evolucionaron a enfermedad renal crónica.

IgM nephropathy is a rare disease with variable clinical presentations and is an unusual cause of nephrotic syndrome. Histopathological findings typically include mesangial hypercellularity with IgM and complement deposition, though the spectrum may range from normal glomeruli through to focal and segmental glomerulosclerosis. Thromboembolism is a well recognised complication of nephrotic syndrome, but cerebral venous sinus thrombosis is rarely described.
This is the case of a 23-year-old male presenting with the nephrotic syndrome, whose initial renal biopsy was consistent with minimal change disease. Complete remission was achieved with prednisone, however multiple relapses and steroid dependence prompted re-biopsy, the results of which were more consistent with IgM nephropathy. His last relapse was complicated by cerebral venous sinus thrombosis. He then received rituximab and a weaning course of prednisone to again enter remission.
This case highlights the need to consider IgM nephropathy in the differential diagnosis of nephrotic syndrome. Additionally, it emphasises the risk of thrombosis in patients with severe nephrosis.

Nintedanib, a triple tyrosine kinase inhibitor of vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and fibroblast growth factor receptor, has been used in idiopathic pulmonary fibrosis and adenocarcinoma in advanced non-small cell lung cancer. Although vascular endothelial growth factor inhibitors have been reported to cause endothelial injury and glomerular microangiopathy, nintedanib-induced glomerular microangiopathy has not been reported. A 68-year-old man with a history of primary aldosteronism, idiopathic pulmonary fibrosis, and pleomorphic carcinoma of the lung developed proteinuria and leg edema after nintedanib initiation. Kidney biopsy revealed prominent endothelial and mesangial injury. Proteinuria improved after nintedanib withdrawal. To the best of our knowledge, this is the second case report of nintedanib-induced glomerular microangiopathy. Although the incidence of nephropathy among patients receiving nintedanib is unknown at this moment, we recommend monitoring urinary protein excretion and blood pressure in patients receiving nintedanib and performing kidney biopsy to determine any histopathological change.

Ustekinumab (UST), an interleukin (IL)-12/IL-23-blocking monoclonal antibody, is a novel therapeutic option for Crohn\'s disease (CD). We describe a 24-year-old man with CD who showed an abrupt decline in renal function after administration of UST. Twenty-nine months previously, the patient was diagnosed with CD, and abnormal urinalysis findings in health checkup were coincidentally found at that time. Three months previously, treatment for CD was switched from infliximab to UST because of therapy-resistant severe diarrhea and bloody stools. A single dose of UST (260 mg) was initially intravenously administered, followed by single subcutaneous administration (90 mg) 2 months later. Thereafter, the patient exhibited rapid renal dysfunction with significant urinary abnormalities, although his gastrointestinal symptoms had completely disappeared. He was admitted to our hospital for further examination and treatment. Renal pathologic findings were compatible with crescentic glomerulonephritis consisting of almost fibro-cellular crescents. Immunofluorescent study showed IgA and C3 deposition in the glomerular mesangial area and IgA subclass staining revealed predominant IgA1 with concomitant mild IgA2 deposition. Furthermore, galactose-deficient IgA1 (Gd-IgA1) was also positive in the mesangial area. In addition, serum-Gd-IgA1 level was moderately increased. UST treatment was stopped and he responded to intensive steroid therapy with a parallel reduction of serum creatinine and Gd-IgA1 levels without flare of gastrointestinal symptoms. To our knowledge, this is the first case of immunoglobulin A nephropathy (IgAN) in patient with CD that might be aggravated by UST treatment. We presume that inhibition of IL-12/23 signaling with UST may cause to form crescentic IgAN by enhancing Gd-IgA1 production.

Heavy chain deposition disease (HCDD) is a rare consequence of monoclonal immunoglobulin deposition disease that has not been well characterized in non-white populations. To explore the clinicopathologic characteristics and outcomes of HCDD in Chinese individuals, we report on a case series assembled in a single center in China.
Case series.
25 patients with biopsy-proven HCDD were studied retrospectively.
14 men and 11 women with an average age of 50.3 years were studied. The patients presented with hypertension (76%), edema (96%), anemia (84%), serum creatinine level > 1.2mg/dL (68%), nephrotic-range proteinuria (56%), and microscopic hematuria (80%). One (4%) patient had multiple myeloma diagnosed. Serum immunofixation electrophoresis showed that 10 of 21 (48%) patients were positive for monoclonal immunoglobulin. Hypocomplementemia of C3 was found in 68% of patients. Nodular mesangial sclerosis was identified in all patients by using light microscopy. Using immunofluorescence, all 25 patients had deposition of heavy chains of immunoglobulin G class (γ1, 13; γ2, 2; γ3, 6; γ4, 2; γ1 and γ4, 1; and γ2 and γ4, 1). During an average of 40.1 months of follow-up of 20 patients, 65% had improved kidney function, 10% had worsening kidney function, and 25% progressed to kidney failure. Mean values for kidney and patient survival were 37.8 and 40.1 months, respectively. Kidney survival was higher among patients who received chemotherapy.
Retrospective study, single-center experience.
In this case series of HCDD in a single center in China, the heavy chain deposits seen in the kidney biopies of all individuals were of immunoglobulin G class. Chemotherapy improved kidney function, especially among individuals in an early stage of the disease.

To investigate the clinicopathological characteristics of renal damage caused by long-term exposure to carbon disulfide (CS2) in nine patients.
All the patients underwent ultrasound-guided renal biopsy. All specimens were examined by light microscopy and immunohistochemistry (IHC). Samples form one patient were further analyzed using transmission electron microscopy.
Similar pathological changes were observed in all patients, but the degrees of lesions were different. All cases had moderate to severe nodular mesangial hyperplasia; among these, type \"Kimme1stie1-Wi1son\" (K-W nodule for short) was observed in four cases, type \"K - W nodule\" refer to nodular hyperplasia of mesangial membrane like letter K or W. four cases had proliferative extracapillary glomerulonephritis (GN), while there were no concomitant changes in one patient. Besides, six cases had diffuse basement membrane thickening, focal segmental sclerosis or bulbar sclerosis; two cases had diffuse glomerular sclerosis, and one case had focal segmental capillary hyperplasia. Moreover, all patients had renal tubular atrophy/interstitial fibrosis with less to moderate chronic inflammatory cell infiltration, as well as renal arteriosclerosis. IHC showed that the depositions of IgA, IgM, C3d, C4d, C1q and Fib were not specific; while IgG, type III collagen, Fibronectin, Amyloid A, Igκ, Igλ, HBsAg and HBcAg were all negative.
Diffuse nodular mesangial hyperplasia/sclerosing glomerular nephropathy is characterized by nodular mesangial hyperplasia with type \"K-W nodules\" formation, which we speculate is a special pathological manifestation of renal damage caused by carbon disulfide (CS2).

Anti-glomerular basement membrane (GBM) glomerulonephritis does not usually coexist with another glomerulonephritis such as IgA nephropathy. We present a rare case having a combination of these two diseases, and furthermore, histological evaluation could be performed before and after the development of anti-GBM glomerulonephritis over a period of only10 months.
A 66-year-old woman was admitted with complaints of microscopic hematuria and mild proteinuria for the past 3 years. Serum creatinine level was normal at that time. The first renal biopsy was performed. Light microscopy revealed mesangial proliferative glomerulonephritis with fibro-cellular crescents in one out of 18 glomeruli, excluding one global sclerotic glomerulus. Immunofluorescence (IF) showed IgA and C3 deposition in the mesangium. Therefore, the diagnosis was IgA nephropathy. Eight months later, the patient\'s serum creatinine suddenly rose to 4.53 mg/dL and urinalysis showed 100 red blood cells per high power field with nephrotic range proteinuria (12.3 g/gCr). The serological tests revealed the presence of anti-GBM antibody at the titer of 116 IU/mL. Treatments were begun after admission, consisting of hemodialysis, plasma exchange, and intravenous methylprednisolone pulse therapy. At 4 weeks after admission, the second renal biopsy was performed. Light microscopy revealed crescents in 18 of 25 glomeruli, excluding six global sclerotic glomeruli. IF showed linear IgG deposition along the GBM in addition to granular IgA and C3 deposition. Based on these findings, the diagnosis of anti-GBM glomerulonephritis and IgA nephropathy was confirmed. Renal function was not restored despite treatment, but alveolar hemorrhage was prevented.
We report a patient with a diagnosis of anti-GBM disease during the course of IgA nephropathy. This case strongly suggests that the presence of autoantibodies should be checked to rule out overlapping autoimmune conditions even in patient who have previously been diagnosed with chronic glomerulonephritis, such as IgA nephropathy, who present an unusually rapid clinical course.

BACKGROUND: Acute renal failure developing over a short period of time with evidence of glomerular disease by urine sediment microscopy characterizes the clinical syndrome of rapidly progressive glomerulonephritis (RPGN), of which the most common causes are ANCA-associated glomerulonephritis (GN), immune-complex mediated GN and anti-GBM disease.
METHODS: This was a middle-aged gentleman who presented with acute renal failure and a positive PR3-ANCA.
METHODS: Renal biopsy showed an unusual combination of PR3-ANCA GN with focal crescents, monoclonal immunoglobulin deposition disease (MIDD) and mesangial IgA deposition on renal biopsy.
METHODS: Serum and urine protein electrophoresis (UPEP) and immunofixation showed no detectable monoclonal paraprotein; bone marrow biopsy was negative for plasma cell neoplasia. He received high dose steroids and rituximab.
RESULTS: The patient did not respond to treatment and progressed to end-stage renal failure within 2 months after presentation.
CONCLUSIONS: To our knowledge, the simultaneous occurrence of MIDD, PR3-ANCA and mesangial IgA has not been reported. This case highlights not only the diagnostic but also the therapeutic challenges that such a complex case presentation poses to clinicians, where the culprit may not always be what would seem most obvious (such as ANCA in a patient with RPGN) but may, in fact, be an underlying and unsuspected disease, or possibly a combination of both.