Immunohistochemical Expression of Antitissue Transglutaminase 2 in Tissue Injuries: An Interpretation Beyond Celiac Disease

Tissue transglutaminase 2 enzyme plays a diverse role in intracellular and extracellular functioning. Aberrant expression of anti-TG2 antibody has recently been proposed for extraintestinal identification of celiac disease (CeD), but its utility is questionable. To examine whether anti-TG2 immunohistochemical (IHC) staining can be of diagnostic value in identifying extraintestinal involvement in CeD, tissue blocks of patients with IgA nephropathies (IgAN), minimal change disease, membranous glomerulonephritis, membrano-proliferative glomerulonephritis, normal kidney, intestinal biopsies from CeD, tropical sprue, nonspecific duodenitis, and inflammatory bowel disease; liver biopsies from patients with chronic hepatitis B and C, acute liver failure (ALF), and CeD-associated liver diseases were retrieved and subjected to IHC staining for antitissue transglutaminase 2 enzyme. H-score was calculated by multiplying the area of positivity and stain intensity. Anti-TG2 stain H-scores were almost similar in IgAN and non-IgANs (H-score 6.31 +/- 3 vs. 7.03 +/- 2.7); however, H-scores in both of these groups were significantly higher than in normal renal parenchyma (1.6 +/- 1.5). Only 6.2% patients with IgAN with anti-TG2 immunostain positivity showed a positive anti-tTG antibody serology and villous abnormalities, suggestive of CeD. Intestinal biopsies from patients with CeD, tropical sprue, nonspecific duodenitis, and inflammatory bowel disease also showed high anti-TG2 H-scores, with no statistically significant differences. Liver biopsies from patients with both ALF, as well as chronic liver diseases showed high anti-TG2 H-scores; with highest stain expression in ALF. In conclusion, IHC expression of anti-TG2 stain correlates with both acute and chronic tissue injuries, irrespective of etiology and organ involvement. It is not a reliable marker for diagnosis of CeD.