Immunoglobulin G (IgG) is an antibody isotype secreted by plasma cells and composed of four peptide chains – two identical heavy chains and two identical light chains arranged in a Y-shape typical of antibody monomers (1). In humans, IgG consists of four subclasses that differ only marginally in their amino acid composition (1). Representing approximately 75% of serum immunoglobulins in humans, IgG is the most abundant antibody isotype found in the circulation (1). Anti-IgG had been proven useful in the assessment of renal biopsies (2), autoimmune disorders (3), in the identification of plasma cell neoplasms (4) and in non-Hodgkin lymphomas (5). The ratio of IgG4+ plasma cells to IgG+ plasma cells has been considered important in making a diagnosis of IgG4-related disorders (6).