Renal involvement is very common in patients with HIV infection. The phenotype varies from the most frequently \"collapsing\" variant of focal and segmental glomerulosclerosis (FSGS) to \"lupus-like HIV-immune complex kidney disease\" (HIVICK). The latter is characterized by a histological picture that recalls lupus nephropathy. Through a clinical case, we underline the importance of urinary sediment analysis in patients with suspected glomerulopathy. Findings such as the characteristic cells that show the typical appearance of Herpes virus (HSV) infection or LE cells have significantly supported the diagnosis of HIVICK. In light of the present observations, we suggest systematically carrying out a cytological examination of the urinary sediment to confirm diagnostic hypotheses of rare pathologies.

Following allogenic hematopoietic stem cell transplantation (HSCT), graft-versus-host disease (GVHD) may develop which may affect several organs. Although the presence of nephrotic syndrome after HSCT is rare, sometimes it occurs in the setting of GVHD. The most common histological finding on kidney biopsy of patients with proteinuria owing to GVHD is membranous glomerulonephritis (MGN). However, reports of immune complex deposition in the tubular basement membrane (TBM) and glomerular basement membrane (GBM) are extremely rare. Herein we present a 65-year-old female with a history of HSCT at six years ago who was referred to Dr.Shariati Hospital in Tehran with nephrotic syndrome. Secondary serologic laboratory tests were all normal. The histopathologic study indicated diffuse GBM and TBM thickening, spike formation, infiltration of inflammatory mononuclear cells in tubulointerstitial area and acute tubular injury in light microscopy. Immunofluorescence staining showed immune complex deposits in GBM, mesangial cells, and TBM.  DOI: 10.52547/ijkd.7550.

Q fever is a zoonosis caused by the intracellular gram-negative bacterium Coxiella burnetii. Infection can be asymptomatic, acute or can cause chronic disease. Chronic disease often presents with infective endocarditis (IE). Diagnosis of IE is difficult because the agent does not grow easily in standard blood cultures and valve vegetations are difficult to detect. Glomerular involvement in patients with Q fever endocarditis is limited to the case reports. In addition, a total of three cases of Q fever endocarditis from Türkiye have been published so far. In this case report, a fourth case of Q fever endocarditis from Türkiye accompanied by immune complex-mediated glomerulonephritis was presented. A 35-year-old male patient with a history of mitral and aortic heart valve replacement was admitted with complaints of fever, night sweats and involuntary weight loss. Cervical lymphadenopathy and hepatosplenomegaly were found during the examination. Laboratory investigations revealed anemia inflammation, acute kidney injury (AKI), hematuria and proteinuria. While no causative agent was detected in blood and urine cultures, no diagnosis could be made as a result of bone marrow and cervical lymph node biopsies.Transesophageal echocardiography was performed for the etiology of fever and revealed 7 mm vegetation on the prosthetic mitral valve. C.burnetii phase 1 IgG tested with indirect immunofluorescent antibody method was reported positive at 1/16384 titer and doxycycline and hydroxychloroquine treatments were initiated. Kidney biopsy for the etiology of AKI revealed focal segmental endocapillary proliferative glomerulonephritis with C3, C1q and IgM immunocomplex deposition. After the addition of methylprednisolone to the treatment, the patient\'s symptoms improved and creatinine and proteinuria levels decreased dramatically. Although Q fever is endemic in our country, it is detected in fewer numbers than expected. In addition to the difficulties in microbiological and clinical diagnosis, the low awareness of physicians about the disease is one of the important reasons for this situation. When the disease comes to mind, the diagnosis can be easily reached by serological methods. Therefore, Q fever should be investigated in the presence of lymphoproliferative disease-like findings fever of unknown origin and culture-negative endocarditis.

Rare cases of immunoglobulin G (IgG)-dominant immune complex-mediated glomerulonephritis demonstrate immunoglobulin subclass restriction without light chain restriction. Some of these cases may represent proliferative glomerulonephritis with monotypic immunoglobulin deposits (PGNMID) in which monotypic immunoglobulin is obscured by coexisting polytypic immunoglobulin. However, rigorous demonstration of this possibility is lacking to date. Here, we describe a case of IgG3-restricted immune complex-mediated glomerulonephritis without light chain restriction that apparently \"transformed\" into IgG3κ-PGNMID in a subsequent biopsy. We demonstrate, using several ancillary techniques, including use of the newly described antibodies directed against the conformational epitope at the junctions of heavy and light chains (HLC-IF), that the first biopsy likely represents IgG3κ-PGNMID in which monotypic IgG3κ was hidden by polytypic IgM. This case underscores the need to consider PGNMID in a differential diagnosis of IgG-dominant immune complex-mediated glomerulonephritis without light chain restriction and highlights the potential utility of IgG subclass staining and HLC-IF in such cases to detect monotypic immunoglobulin that may be obscured by coexisting IgM and/or IgA deposits.

We report the first case of immune complex type hemolytic anemia by initial micafungin administration that was given as prophylaxis to a 42-year-old Japanese man receiving chemotherapy for primary amyloidosis. The few cases found in the literature were associated with secondary administration causing immune hemolytic attacks. Despite its rarity, the present case calls for increased awareness of micafungin-induced hemolytic anemia upon initial administration.

Infective endocarditis (IE) may be misdiagnosed as ANCA-associated vasculitis (AAV), especially when antineutrophil cytoplasmic antibodies (ANCA) are detected. Distinguishing IE from AAV is crucial to guide therapy. However, little is known about ANCA positivity in IE patients. We present a case report and systematic review of the literature on patients with ANCA-positive IE, aiming to provide a comprehensive overview of this entity and to aid clinicians in their decisions when encountering a similar case. A systematic review of papers on original cases of ANCA-positive IE without a previous diagnosis of AAV was conducted on PubMed in accordance with PRISMA-IPD guidelines. A predefined set of clinical, laboratory, and kidney biopsy findings was extracted for each patient and presented as a narrative and quantitative synthesis. A total of 74 reports describing 181 patients with ANCA-positive IE were included (a total of 182 cases including our own case). ANCA positivity was found in 18-43% of patients with IE. Patients usually presented with subacute IE (73%) and had positive cytoplasmic ANCA-staining or anti-proteinase-3 antibodies (79%). Kidney function was impaired in 72%; kidney biopsy findings were suggestive of immune complexes in 59%, while showing pauci-immune glomerulonephritis in 37%. All were treated with antibiotics; 39% of patients also received immunosuppressants. During follow-up, 69% of patients became ANCA-negative and no diagnosis of systemic vasculitis was reported. This study reviewed the largest series of patients with ANCA-positive IE thus far and shows the overlap in clinical manifestations between IE and AAV. We therefore emphasize that clinicians should be alert to the possibility of an underlying infection when treating a patient with suspected AAV, even when reassured by ANCA positivity. Key Points • This systematic review describes - to our knowledge - the largest series of patients with ANCA-positive infective endocarditis (IE) thus far (N=182), and shows a high degree of overlap in clinical manifestations between IE and ANCA-associated vasculitis (AAV). • ANCA positivity was found in 18-43% of patients with infective endocarditis. Of patients with ANCA-positive IE, the majority (79%) showed cytoplasmic ANCA-staining or anti-PR3-antibodies. We emphasize that clinicians should be alert to the possibility of an underlying infection when treating a patient with suspected AAV, even when reassured by ANCA positivity. • In patients with IE and ANCA-associated symptoms such as acute kidney injury, an important clinical challenge is the initiation of immunosuppressive therapy. All patients with data in this series received antibiotics; 39% also received immunosuppressive therapy. In many of these patients, ANCA-associated symptoms resolved or stabilized after infection was treated. ANCA titers became negative in 69% , and a diagnosis of AAV was made in none of the cases. We therefore recommend that (empiric) antibiotic treatment remains the therapeutic cornerstone for ANCA-positive IE patients, while a watchful wait-and-see approach with respect to immunosuppression is advised.

Childhood IgA nephropathy (cIgAN) is one of the most common primary glomerulonephritides with the potential to evolve to kidney failure. IgAN is an autoimmune disease involving 3 key factors: galactose-deficient IgA1 (Gd-IgA1), anti-IgA1 autoantibodies, and soluble (s)CD89 IgA Fc receptor. These molecules and immune complexes have been described recently as potential biomarkers of disease progression in childhood IgAN but their evolution in time under immunosuppressive treatment remains unknown.
We performed a prospective study of two proliferative cIgAN patients by sequentially biomonitoring immune IgA complexes (sCD89-IgA, IgG-IgA), sCD89, and Gd-IgA1 and correlating them with clinical and histological outcome after treatment.
After patient 1\'s treatment, a decrease in sCD89-IgA, IgG-IgA, and free sCD89 was linked to a decrease in proteinuria whereas eGFR (estimated glomerular filtration rate) and Gd-IgA1 levels remained stable. Patient 1 received tacrolimus and monthly intramuscular steroid injections of Kenacort for 10 months. At the end, a relapse induced an increase in proteinuria consistent with an increase of the 3 biomarkers. Patient 2 displayed rapidly progressive IgAN with crescents in more than 90% of glomeruli and received intense immunosuppression treatment associated with the immunoadsorption (IA) approach. During IA, proteinuria decreased rapidly, as well as levels of CD89-IgA, IgG-IgA, sCD89, and Gd-IgA1 biomarkers. After discontinuation of IA, proteinuria increased as well as IgG-IgA complexes whereas sCD89-IgA and sCD89 remained low. Further re-intensification of IA and addition of cyclophosphamide improved proteinuria again with reduced IgG-IgA. A second biopsy was performed showing a reduction of extracapillary proliferation to 6% of glomeruli and only 9% glomerulsoclerosis.
In conclusion, sequential biomonitoring of Gd-IgA1, IgA-immune complexes, and sCD89 in cIgAN was found to be valuable, by correlating with clinical features and glomerular proliferative lesions in cIgAN. These biomarkers could represent useful tools to evaluate kidney injury without repeat kidney biopsies.

BACKGROUND: Cases of immune complex vasculitis have been reported following COVID-19 infections; so far none in association with novel mRNA-based COVID-19 vaccination. This case report describes a cutaneous immune complex vasculitis after vaccination with BNT162b2.
METHODS: A 76-year old male with liver cirrhosis developed an immune complex vasculitis 12 days after the second injection of BNT162b2. On physical examination, the patient presented with pruritic purpuric macules on hands and feet, flexor and extensor parts of both legs and thighs and lower abdomen, and bloody diarrhoea. Laboratory testing showed elevated inflammatory markers. After short treatment with oral steroids all clinical manifestations and laboratory findings resolved.
CONCLUSIONS: An increasing number of clinical manifestations have been attributed to COVID-19 infection and vaccination. This is the first written report of immune complex vasculitis after vaccination with BNT162b2. We present our case report and a discussion in the light of type three hypersensitivity reaction.

We studied the stability of two salt bridges between hen egg-white lysozyme (HEL) and its antibody, HyHEL-10, by using molecular dynamics simulations. It was observed that one salt bridge, D32H-K97Y, was stable, whereas the other, D99H-K97Y, was not. To understand this difference, we compared several reduced salt bridge models that incorporated the salt bridges and nearby residues. The results showed the importance of nearby residues, especially Y33H and W98H. Furthermore, to understand the effects of nearby salt bridges, we investigated two mutants, D32HA and D99HA. We found that the D32HA mutation considerably stabilized the D99H-K97Y salt bridge. The reduced model analysis indicated that this can be largely attributed to a conformational change of the main chain.

The systemic manifestations of immunoglobulin A (IgA) nephropathy with lung involvement include diffuse alveolar hemorrhage due to monoclonal IgA disorders, IgA-variant Good pasture\'s syndrome, and Henoch-Schoenlein purpura. However, pneumonitis due to IgA immune complex has rarely been reported as the pulmonary manifestations of IgA nephropathy.
A 35-year-old woman presented with 2 years of progressive shortness of breath, dry cough, low-grade fever along with progressive loss of appetite, and loss of weight. She underwent renal, duodenal, and lung biopsies. She was diagnosed with a rare combination of IgA-mediated nephropathy, IgA-associated celiac disease, and IgA-mediated immune complex cavitary lung disease.
Secretory IgA may be acting as an immune complex or proinflammatory agent to provoke the signs and symptoms in this case. Thus, the respiratory process may incite renal disease or vice-versa. Further research is needed to analyze the possibility of such associations.