11-year-old Boy With Retrosternal Chest Pain

Chest X-Ray of 11-year-old boy with retrosternal chest pain

An 11-year-old previously healthy boy presented to the emergency department complaining of a three week history of intermittent sharp retrosternal chest pain. He did not report any other features on further questioning.

His initial observations were within normal limits; however, he had a low-grade pyrexia of 37.6. Cardiovascular examination was unremarkable and his electrocardiogram showed no acute changes. Abdominal examination revealed non-tender hepatosplenomegaly. Respiratory examination revealed no abnormality.

What could be the diagnosis ?