A 11-year-old boy of Congolese descent, born in Belgium and without significant medical history, presented with nonbloody diarrhoea for several weeks and unintentional weight loss. He reported a recent history of rhinitis and coughing with spontaneous improvement. He received all of his recommended vaccines (BCG vaccine not included) and he never left Belgium. The family history indicated no documented cases of TB or recent visits to a country with a high burden of TB. Physical examination was normal. Laboratory investigations showed a mild microcytic anaemia and slightly elevated inflammatory markers; sedimentation 29 mm/hr (normal range 0-13 mm/hr), and C-reactive protein level 16 mg/L (normal range <3 mg/L). Chest X-ray demonstrated minimally reduced lung translucence with possible ground-glass opacity, but an additional CT-thorax was unremarkable. The tuberculin skin test (TST) and the interferon-gamma release assay (IGRA), executed with T.SPOT.TB, were also negative. Abdominal ultrasound demonstrated discrete wall thickening of the terminal ileum with accompanying mesenteric lymphadenitis (four enlarged lymph nodes noted, the largest 27 x 16 mm). One week after presentation, he was referred for a colonoscopy because of markedly elevated faecal calprotectin of 4735 mg/kg (normal range <50 mg/kg) which is indicative of bowel inflammation.