Abstract: In most cases，it is very difficult for clinician to diagnosis Crohn disease(CD) because the atypical or overlapped colonoscopic manifestations with other diseases. Especially， it is a great challenge to distinguish CD from intestinal tuberculosis(ITB) in clinical practice because the two diseases share the same location，confusingly similar clinical manifestations， and sometimes similar endoscopic features. The differentiation between CD and ITB mainly relies on the comprehensive analysis of pathology and extraintestinal manifestations if the lesion is atypical endoscopically. Another misdiagnosed situation of CD is intestinal lymphoma， because it is quite difficult to make a conclusion to lymphoma via a singe biopsy pathology，  which is related to the biopsy specimens and experiences of pathologists. Therefore， multiple sites biopsy and careful pathological examination (if necessary， immunohistochemistry， gene rearrangement or in situ hybridization) serve the key to avoid the misdiagnosis and missed diagnosis of lymphoma. In addition， the atypical lesions of CD should also be ruled out of intestinal Behcet disease，nonsteroidal antiinflammatory drugs(NSAIDs) related enteropathy and other rare causes of enteropathies through a combination of repeated biopsy pathology and specific clinical features.

Key words: Crohn disease；diagnosis；diagnosis, differential