A Case of Colonic Tuberculosis Revealed by Polymerase Chain Reaction

The authors report a case of tumor-like colonic tuberculosis revealed by PCR in a 32-year-old patient with a low-level peritoneal effusion on CT scan with negative histological study on colonic biopsy.

The colonic biopsy received at the laboratory after grinding in a porcelain mortar, was the object of a molecular study by GeneXpert MT/RIF (Cepheid, Sunnyvale, CA, USA) using the automated real-time PCR technique and a conventional study based on Ziehl-Nielsen staining and culture on Lowenstein-Jensen® solid medium (LJ) and Mycobacteria Growth Indicator Tube (MGIT®) liquid medium.

The patient was a 32-year-old male without any personal or family history of tuberculosis and without signs of tuberculosis impregnation. He had a story of ingestion of non-pasteurized dairy products including milk and cheese. For 45 days he had constipation with abdominal pain and feeling of heaviness. Physical examination of the patient revealed abdominal tenderness without adenopathy. The laboratory workup showed a normal blood count, CRP, liver and kidney function tests. The HIV test was negative. Medical imaging revealed a low-level peritoneal effusion that could not be punctured. Colonoscopy showed a thickening of the colon. The colonic biopsy, after crushing and sonication, was searched for the Mycobacterium tuberculosis complex by both molecular biology and conventional methods. Molecular research by GeneXpert MTB/RIF (Cepheid, Sunnyvale, CA, USA) using the automated real-time PCR technique, revealed the presence of the Mycobacterium tuberculosis complex without detection of rifampicin resistance. On the other hand, the direct examination after special Ziehl-Nielsen staining was positive (Figure 2) and the cultures on Lowenstein-Jensen® solid medium (LJ) and Mycobacteria Growth Indicator Tube (MGIT®) liquid medium were also positive after two and three weeks, confirming the molecular diagnosis. The histology study showed moderate non-specific chronic colitis with no histological arguments for tuberculosis or malignancy. The patient was placed on curative tuberculosis treatment according to the national protocol, with a favorable clinical-radiological course.

Colonic tuberculosis is a disease that may mimic many other diseases; therefore, a correct approach is necessary for the correct diagnosis and treatment.