Persisting and emerging areas of diagnostic difficulty in the histopathology of infectious disease of the gastro-intestinal tract

In the five years since the last themed issue of Diagnostic Histopathology on Infectious Diseases, the development of molecular diagnostics for infectious disease has ushered in a revolution in this field, and some examples in gastro-intestinal (GI) histopathology are discussed in this article. Despite these advances, one of the most ancient and prevalent of infectious diseases world-wide, tuberculosis, remains one of the most taxing clinico-histopathological diagnostic dilemmas, and three challenging cases in the GI system are briefly discussed to illustrate the point. Another area of interpretive difficulty that has emerged in the last few years is that of primary immunological disorders and the side-effects of immunotherapies, both of which display a complex interplay with GI tract infections, spanning diagnostics and therapeutics. These, as well as the controversial entities of 'autoimmune enteropathy' and 'Human Immunodeficiency Virus (HIV) enteropathy', all of which share overlapping histological features, are discussed.