Israel Medical Association Journal

Inborn errors of immunity (IEI) result from pathogenic germline variants. These disorders are clinically characterized by increased susceptibility to infections and immune dysregulation, often leading to reduced survival [1]. By linking specific monogenic defects to immune phenotypes, IEI serve as experiments of nature that provide powerful models for dissecting human immunology [2]. The International Union of Immunological Societies (IUIS) currently classifies IEI into 10 major categories with overlapping phenotypes [3]: combined T- and B-cell immunodeficiencies, combined immunodeficiencies with syndromic features, predominantly antibody deficiencies, diseases of immune dysregulation, congenital defects of phagocytes, defects in intrinsic and innate immunity, autoinflammatory diseases, complement deficiencies, bone marrow failure, and phenocopies of IEIs. The recent 2024 IUIS update was designed to serve clinicians and researchers and to inform the design of targeted sequencing panels that facilitate the genetic diagnosis of IEI. It lists 508 genes underlying 559 conditions [3]. Of note, molecular, cellular, and clinical investigations of IEI have transformed our understanding of disease pathogenesis and enabled effective targeted therapies.

Background: Anti-glomerular basement membrane (GBM) antibody disease, or Goodpasture’s disease, is the clinical manifestation of the production of anti-GBM antibodies, which causes rapidly progressive glomerulonephritis with or without pulmonary hemorrhage. Anti-GBM antibody detection is mandatory for the diagnosis of Goodpasture’s disease either from the serum or kidney biopsy. Renal biopsy is necessary for disease confirmation; however, in cases in which renal biopsy is not possible or is delayed, serum detection of anti-GBM antibody is the only way for diagnosis.

Objectives: To assess the predictive value of positive anti-GBM antibodies in a clinical setting. 

Methods: Data from anti-GBM antibody tests performed at one medical center between 2006 and 2016 were systematically and retrospectively retrieved. We recruited 1914 patients for the study. Continuous variables were computed as mean ± standard deviation, while categorical variables were recorded as percentages where appropriate. Sensitivity and specificity of anti-GBM titers were calculated. Kaplan–Meyer analysis was performed, stratifying survival according to the anti-GBM antibody titers.

Results: Of the 1914 anti-GBM test results detected, 42 were positive, 23 were borderline, 142 were excluded, and 1707 results were negative. Male-to-female ratio was 1:1.2. Sensitivity of anti-GBM test was 41.2% while specificity was 85.4%. Concerning the Kaplan–Meyer analysis, overall survival was 1163.36 ± 180.32 days (median 1058 days). 

Conclusions: Our study highlights the lack of sensitivity of serological testing of anti-GBM titers. Comparing survival curves, the survival correlated with anti-GBM titer only in a borderline way. Because highly sensitive bioassays are not routinely used in clinics, renal biopsy is still pivotal for Goodpasture’s disease diagnosis.

 

Anti-neutrophil cytoplasm antibodies are important markers of certain small vessel necrotizing vasculitides, but the optimal use of laboratory results in daily clinical practice necessitates collaboration between clinicians and laboratory specialists. Physicians must familiarize themselves with ANCA tests in ANCA-related vasculitides as well as in differential diagnostic patient populations in order to define cutoff values. Indirect immunofluorescence with a consensus-agreed technique combined with standardized enzyme immunoassays is the modality for detecting the main SSV-associated ANCA specificities using cutoff values that can sufficiently distinguish SVV from non-SVV patients. The combined use of IF and direct EIA to demonstrate proteinase 3-ANCA and myeloper­oxidase-ANCA at significant levels leads to a very high diagnostic specificity towards SVV conditions such as Wegen­er’s granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome, and limited forms of these such as renal-limited focal necrotizing glomerulonephritis. A strong reactivity of ANCA against several azurophil granule components indicates a drug-induced syndrome. ANCA-related SVV and drug­induced vasculitis or lupus syndromes have characteristic ANCA profiles that can help distinguish these conditions from other inflammatory diseases.