Falsely positive anti-glomerular basement membrane antibodies in a patient with hantavirus induced acute kidney injury - a case report

Anti-GBM antibody in a patient with diabetic nephropathy; all that glitters is not gold

We present the case of a 58-year-old male diabetic patient admitted to our department for a slight decrease in kidney function, with nephrotic range proteinuria, hematuria (16,000/ml) and positive anti-glomerular basement membrane antibodies. Kidney biopsy revealed diabetic nephropathy with no evidence of crescent formation or linear immunoglobulin deposits along the basement membrane. We discuss the various clinical settings involving positive anti-glomerular basement membrane in the absence of crescentic glomerulonephritis.

Use of a diagnostic Puumala virus real-time RT-PCR in an orthohantavirus endemic region in the Netherlands

Laboratory diagnosis of orthohantavirus infection is primarily based on serology. However, for a confirmed serological diagnosis, evaluation of a follow-up serum sample is essential, which is time consuming and causes delay. Real-time reverse transcription polymerase chain reaction (RT-PCR) tests, if positive, provide an immediate and definitive diagnosis, and accurately identify the causative agent, where the discriminative nature of serology is suboptimal. We re-evaluated sera from orthohantavirus-suspected clinical cases in the Dutch regions of Twente and Achterhoek from July 2014 to April 2016 for the presence of Puumala orthohantavirus (PUUV), Tula orthohantavirus (TULV), and Seoul orthohantavirus (SEOV) RNA. PUUV RNA was detected in 11% of the total number (n = 85) of sera tested, in 50% of sera positive for anti-PUUV/TULV IgM (n = 16), and in 1.4% of sera negative or indeterminate for anti-PUUV/TULV IgM (n = 69). No evidence was found for the presence of TULV or SEOV viral RNA. Based on these findings, we propose two algorithms to implement real-time RT-PCR testing in routine orthohantavirus diagnostics, which optimally provide clinicians with early confirmed diagnoses and could prevent possible further invasive testing and treatment.

IMPORTANCE

The addition of a real-time reverse transcription polymerase chain reaction test to routine orthohantavirus diagnostics may better aid clinical decision making than the use of standard serology tests alone. Awareness by clinicians and clinical microbiologists of this advantage may ultimately lead to a reduction in over-hospitalization and unnecessary invasive diagnostic procedures.

Renal Medullary Angiitis Associated with Cutaneous Leukocytoclastic Vasculitis

Renal medullary angiitis is characterized by interstitial hemorrhaging in the medulla with neutrophil infiltration. An 81-year-old man presented with a fever, kidney dysfunction, and purpura of the legs, which was diagnosed as leukocytoclastic vasculitis. Proteinase 3 antineutrophil cytoplasmic antibodies were weakly positive. A kidney biopsy showed severe tubulointerstitial hemorrhaging with neutrophilic infiltration in the perivascular areas surrounding the vasa recta in the medulla without crescent formation in the glomeruli. An immunofluorescence analysis was negative, and electron microscopy revealed no immune-dense deposits, ruling out immunoglobulin A vasculitis. Intravenous methylprednisolone for three days and plasma exchange followed by oral prednisolone improved his general condition.

Demonstration of equivocal anti-glomerular basement membrane antibody positivity as a non-specific reaction through multiple immunologic assays in a case of pediatric asymptomatic hematuria

BACKGROUND

Anti-glomerular basement membrane (anti-GBM) antibody is essential for the diagnosis of anti-GBM disease. The major epitope consists of the α3 subunits of type IV collagen non-collagenous domain (α 3(IV)NC1). There have been only a few reports of patients false-positive for anti-GBM antibody.

CASE REPORT

We experienced an 8-year-old boy who presented with asymptomatic hematuria followed by positivity for anti-GBM antibody as evaluated by a commercially available chemiluminescent enzyme immunoassay (CLEIA). While his condition remained stable other than continuing hematuria, his anti-GBM antibody titer increased. Further examination of another anti-GBM antibody assay (fluoroenzyme immunoassay) showed negative results. Thus, evaluation of the accuracy of his positivity for anti-GBM antibody was required. We conducted the following examinations: A) enzyme-linked immunosorbent assay, B) immunoblotting for recombinant α 1-5(IV)NC1, and C) immunohistochemical analysis of normal kidney tissue sections. Specimens used for the analysis were sera in A and IgG from the patient in B and C, respectively. As a result, no anti-GBM antibody was detected in A. In B, no band specific to α 1-5(IV)NC1 was observed. In C, the kidney tissue was not stained. Taken together, these results led us to judge the positive anti-GBM result in CLEIA of our patient to be a non-specific reaction.

CONCLUSION

The commercial assays for anti-GBM antibody can lead to false-positive results. We recommend confirmation of anti-GBM antibody positivity through the use of multiple assays in patients demonstrating an atypical clinical course for anti-GBM disease.

A Case Report of Crescentic Glomerulonephritis With Positive Serum Anti-glomerular Basement Membrane Without Linear Glomerular Basement Membrane Immunofluorescent Staining

Anti-glomerular basement membrane (anti-GBM) disease is an autoimmune disorder characterized by the production of circulating immunoglobulin G (IgG) antibodies that affect the kidneys and lungs, mainly in the form of rapidly progressive crescentic glomerulonephritis and pulmonary hemorrhage. Typically diagnosed on tissue biopsy, findings mainly include glomerular crescent formation, bright linear staining of GBM for IgG on direct immunofluorescence (IF), and the serologic presence of circulating anti-GBM antibodies. Variation in the laboratory results, where histological findings of linear IgG IF staining were present in the absence of circulating anti-GBM antibodies, have recently led to the use of the term “atypical anti-GBM disease,” which usually has a distinct benign clinical outcome as compared to typical anti-GBM disease. We report a case of a middle-aged woman who presented with renal failure without lung involvement. Upon further investigation, the patient was found to have strongly positive serum anti-GBM antibodies, but the tissue biopsy did not show typical findings of the anti-GBM disease. The patient showed modest improvement after multiple sessions of plasmapheresis and steroids, with stabilization of her renal parameters after the initial response. In our case, we will address the possibilities of the discrepancies between the serological and histopathological findings.

Atypical anti-glomerular basement membrane disease complicated by methicillin-susceptible Staphylococcus aureus infection-related rapidly progressive glomerulonephritis: a case report and literature review

Atypical anti-glomerular basement membrane (GBM) disease, which is characterized by low levels of or negativity for anti-GBM antibodies in circulation but positivity in the kidney, has been recognized in this decade. However, a therapeutic strategy has not been established to date because its outcome is better than that of classic anti-GBM disease. This case report and literature review highlight atypical anti-GBM disease in infection-related rapidly progressive glomerulonephritis. A 72-year-old Japanese man diagnosed with methicillin-susceptible Staphylococcus aureus (MSSA)-induced vertebral osteomyelitis experienced for 2 months was referred to our hospital because of renal insufficiency. He developed rapidly progressive glomerulonephritis with a serum creatinine level of 6.8 mg/dL, C-reactive protein level of 9.7 mg/dL, urinary protein-to-creatinine ratio of 3.37 g/gCr, and gross hematuria. The serum anti-GBM antibody concentration was 3.5 U/mL, which was slightly above the normal range (< 3.0 U/mL). Conservative treatment, mainly with antibiotics, improved the symptoms and renal function. The serum anti-GBM antibody concentration peaked at 4.0 U/mL on day 7 and decreased to an undetectable range at the end of eight-week antibiotic therapy. This is the first case report describing the presentation and disappearance of serum anti-GBM antibody in a patient with MSSA infection. Conservative treatment may be effective for patients with atypical anti-GBM disease complicated by infectious diseases.