Clinical interest into the function of tuft cells in human intestine has increased in recent years. However, no quantitative study has examined intestinal tuft cells in pathological specimens from patients. This study quantified tuft cell density by using a recently identified marker, specific for tyrosine phosphorylation (pY1798) of girdin (also known as CCDC88A or GIV) in the duodenum of pediatric patients. Deidentified sections with pathological diagnosis of acute duodenitis, ulcer, or celiac disease, and age-matched normal control were analyzed under double-blind conditions. Immunostaining for pY1798-girdin demonstrated the distinct shape of tuft cells with and filopodia-like basolateral membrane structure and a small apical area, which densely expressed gamma-actin. As compared to normal tissues, the specimens diagnosed as celiac disease and duodenal ulcer had significantly fewer tuft cell numbers. In contrast, acute duodenitis showed varied population of tuft cells. The mucosa with severe inflammation showed lower tuft cell numbers than the specimens with none to mild inflammation. These results suggest that loss of tuft cells may be involved in prolonged inflammation in the duodenal mucosa and disrupted mucosal integrity. pY1798-girdin and gamma-actin are useful markers for investigating the distribution and morphologies of human intestinal tuft cells under healthy and pathological conditions.