Backache: a rare diagnosis and unusual complication.

We report an adolescent girl who presented with an acute exacerbation of a chronic backache of 6 months duration. She complained of dribbling micturition, constipation, and an irresistible urge to strain for 72 h. In the waiting area of the local hospital she developed sudden, severe chest pain with progressive swelling of the upper torso. This proved to be the mode of presentation of a haematocolpos due to an imperforate hymen with the unusual complication of mediastinal emphysema. Imperforate hymen is a rare diagnosis, but should be considered when dealing with an adolescent girl with lower abdominal symptoms or backache.