PA chest shows air-space disease in the right lower lobe, with widening of the para-spinal line (arrow) suggestive of mediastinal lymphadenopathy. Axial CT confirms enlarged paratracheal lymph nodes with hypodense centre (arrows), also visible in the abdomen (arrows).

These findings should suggest tuberculosis as the first possibility. Although TB usually affects upper lobes, involvement of lower lobes should not exclude it.

Final diagnosis: active TB. Congratulations to all of you who made the diagnosis. Muppet believes this was an easy case, considering that most of you made the right diagnosis. The next case will be more difficult because it commemorates Muppet’s 25th anniversary.

Teaching point: lymph nodes with hypodense centre may occur in several processes (treated tumours, Whipple’s, etc.), but in the appropriate clinical situation, the first diagnostic consideration should always be tuberculosis.